The Correct Thread for Minamoto/Taira factions

[tokimitsu]

Acting on Yelu's advice, this thread is opened for modifying some errors of Japanese factions and gathering the correct scripts about Taira and Minamoto.

It seems that Sengoku Jidai(戦国時代 15th~16th)'s military stuffs reflect on that of Japanese factions of AUH.

Sengoku Jidai of the 15~16th century was the revolutionary main turning point of Japanese military history, so we have to seperate Japanese military stuffs of AUH from that of Sengoku Jidai.

To correct these errors, I made this thread.

[tokimitsu]

As for Japanese settlements

I select 12 Settlements finally.
Well, there were no noticeable settlements or cities except Heian Kyo, Fukuhara, Dazaifu, Nara, Kamakura, Hiraizumi in 1180 of Japan.
I suffer from selecting Japanese settlements more than 10, frankly speaking.
So I consulted my Japanese medieval history professor about it.
He had been a professor of Kyoto University.





After that, I selected carefully 12 settlements of Japan.

Spoiler Alert, click show to read: 

For Taira(平) clan : 6 settlements

• Dazaifu(太宰府) Trade and Defend center of all over the Japan
• Aki(安芸)
• Sanuki(讃岐)
• Fukuhara(福原) Tairano Kiyomori constructed this city to trade. He transfered the capital from Heian Kyo to this city in 1179 for a while. Owada no Tomari is its outport.
• Heian Kyo(平安京) The capital city of Japan, where Japanese Emperor lived in. Today's Kyoto.
• Nara(奈良) Old capital city of Japan

For Minamoto(源) clan : 5 settlements

• Echizen(越前)
• Echigo(越後)　
• Kiso(木曽) The base of Minamotono Yoshinaka
• Kamakura(鎌倉) Minamotono Yoritomo's base city. After the Genpei war, Kamakura becomes the central city of Minamoto Shogunate.
• Hitachi(常陸)　

For Fujiwara(藤原) rebel : 1 settlement

• Hiraizumi(平泉)　This city is called as the Kyoto of north-eastern Japan. One family of noble Fujiwara clan migrated to this land and constructed Hiraizumi imitating Heian Kyo.

As for Hiraizumi(平泉) settlement and its Fujiwara rebels;

In 1180, Hiraizumi is not subjected to either Minamoto or Taira of central court.
Hiraizumi has acted like the half-independent country.
Fujiwara family in Hiraizumi sometimes cooperate with Joko(上皇 the pre-Emperor of Japan) and In(院 the court of Joko) to restrain Minamoto clan from its rear.
Hiraizumi have prospered for 150 years as the "Kyoto of east Japan", being blessed with rich natural resources of Dewa and Mutsu.
Hiraizumi is collapsed by Shogun Minamotono Yoritomo in 1189.

So I think it's good to set the settlement of Hiraizumi as a rebel of north-eastern Japan.
This is more accurate situation based on real history.

As for Higo and Owari;

Higo has the largest number of manors in Kyushu. By only this reason, I selected it as a settlement at first.
But I deleted it because it's obvious that Dazaifu ruled all over Kyushu island at that time,
and because if Higo is added, Taira has 7, so we cannot keep valance between Taira and Minamoto.
In Owari, there were no historical records that Owari Kuni and its surrounding provinces had noticeable settlements in them. So I omitted.
According to some records, there was a military camp in Owari. Because Owari was the nodal point of the military operations in the 12th century.

[tokimitsu]

By the way, may I point out and correct the design of Japanese settlements to progress our works constructively?
I saw these images in Japanese Mini preview.

Do you see letters "Tenshukaku(天守閣)" I point out with red colour?
Tenshukaku is the big centeral tower of Japanese medieval castle. I think you know this word.
But,
Tenshukaku didn't exist in the 12th~14th century.
It begin to be constructed from the middle of 16th century. Tenshukaku represents the era of Sengoku jidai(戦国時代 15th~16th).
AUH mod covers 12th~13th century.
These designs are not for AUH, but for Shogun TW's era of Sengoku Jidai.
So these designs seem to entirely reflects that of future generation. But the gap of period is over 300 years.
In addition, these images below in mini preview are not true for AUH mod.

No Daimyo(大名), No Ashigaru(足輕) at that time.

And there were no city-surrouding walls or castles at that time of Japan. No castles nor city walls, never. I bet.
All the cities were opened at that time.
In Genpei War, there were no siege warfares.
AD 1180 is starting year of AUH mod and Japanese Genpei war.
Military fortresses were not in city and not surround the city.
Military fortresses were not permanent ones but temporary things(tents etc).
So they were the bundle of tents or wooden fences, which was located in nodal points of the road or mountains.
They were not made of stones in 12th century.

Stone walls begin to appear in northern Kyushu just after the 1st Mongolian invasion in 1274.
Japanese samurais constructed low and long stone barrier in outskirt of Dazaifu(太宰府) to defend against Mongols and Koreans.
Before 1274, there were no stone walls, nor city fortresses, nor castles with Tenshukaku.

I think these design(with Tenshukaku and city wall or castle)is not historically accurate.
Somewhat odd, sorry to say that.

So I suggest that all the Japanese settlements should be opened when AUH mod starts.
But I think it's good to lacate temporary military camps around the settlements or in the nodal points of road.

As for new Japanese settlements design,
I will post next script with the images of birds-eye-view.

[tokimitsu]

Here are Heian Kyo, Kamakura, Hiraizumi for example

Heian Kyo
No city wall around it, no fortress in it, no castles in it.
The city is opened.
Cross stripe city planning is main feature of this settlement.
The palace where Japanese Emperor lives is located in the middle of northern edge section of the settlement.
Actually Heian Kyo imitated Tang(唐)'s capital Chang An(長安:Today's Xian西安)
But have no city wall around it.

Spoiler Alert, click show to read: 

Kamakura
No city wall around it, no fortress in it, no castles in it.
The city is opened.

Spoiler Alert, click show to read: 

Hiraizumi
No city wall around it, no fortress in it, no castles in it.
The city is opened.

Spoiler Alert, click show to read: 

[tokimitsu]

And these images are for the mansion of Samurais(Yashiki 屋敷) of east Japan, and its manor of the 12th~14th century.
The mansion represents timehonored simplicity of Samurais.

Spoiler Alert, click show to read: 

[tokimitsu]

This post was written by me a year ago.

Until 13th century in Japan, there weren't visible castles except the low stone barriers or wooden fences.

The famous castles such as Himeji, Nijo, Osaka, Nagoya Castles etc. were built in 16th century of Sengoku Jidai(The Era of the Great civil war)

Why Japanese didn't build the catsle until the 13th century?

Because Japan had been isolated from East-Asian Continent in military terms by the 13th century AD, before Mongolian Invasion.

Before Mongolian Invasion, there was no Group tactics even in battle.
One to one tactics was the battle style of Samurais.
(At this time, Samurais hardly wielded their Katanas in the battle.
They mainly fought with Bows and Arrows just like this illustration below.)

Spoiler Alert, click show to read: 

The typical Samurai in Medieval Japan was the Archer Cavalry, not Katana-wielding Samurai
The stereotype of Katana-wielding Samurai was made after Sengoku Jidai Era in 16th century

Even in Genpei War(Taira vs.Minamoto) of the 12th century, there was no siege battle, either.

Although within 200 years after Mongolian Invasions, Japanese didn't constructed noticeable castles.

But,
15th century of Civil War forced Japanese people to construct the castles or fortresses.
In Civil war of 15th century, Group tactics began to used,
and Ashigaru(light Infantrymen) began to play active parts.
Group tactics influenced the construction of the Castles(Shiro) in Medieval Japan.

So, there were no visible castle(Shiro) in Medieval Japanese Islands of 12th~13th century.

Of course, the cities were not surrounded by the barriers or Castles.
All of the Japanese cities were opened at that time.

[Yelü Dashi]

As usual tokimitsu, your research is faultless. I guess we have quite a bit of work to do to redesign the settlements, but we can use elements from the Chinese strat models. I found some more images for the palace at Heian-kyo, I guess it also had a Tang-era style:

Spoiler Alert, click show to read: 

please do offer your suggestions for the roster - importantly what unique units do the taira and minamoto possess - or do their rosters need to be similar. regarding the fuijiwara, will their units have a different look too ? Also for the Sohei at Nara and Mt Hiei - how do we represented them ? - as rebels that need to be conquered by either factions ? Perhaps as a kind of sub-faction?

[tokimitsu]

Thank you for your compliment. But mine is not so perfect. Maybe there would be faults a little bit in my research. So I have to check my works again and again to find invisible faults.
Where did you get these nice detailed images of Heian Kyo? Very nice images

As for Units
At a moment now what I think is like this;

1.
Sohei(僧兵) should be recruited in the settlements of Heian Kyo and Nara.
Temple Enryakuji(延暦寺) of Mt Hieizan(比叡山) and Temple Kofukuji(興福寺) was mostly famous for Sohei.
These 2 big temples have own Soheis.
Enryakuji locates in outskirt of Heian Kyo and Kofukuji is in Nara.
Around these region of Hean Kyo and Nara, there are many temples which have own Soheis.

So I think it's good that the faction which occupy one of Heian Kyo and Nara can recruit Sohei in AUH.
In the begining of AUH campaign, Taira can recruit Soheis. But if Minamoto occupy these region, Minamoto can recruit Soheis.
Sohei should be recruited only in these 2 settlements : Heian Kyo and Nara

2.
And Taira, Minamoto and Fujiwara's rosters should be similar. Some Units(1 or 2) should have unique unit, I think at a moment now.
About this, I can judge in detail after I check the present Unit Roster.

3.
Fujiwara need to be conquered especially by Minamoto faction, because Hiraizumi is rich with natural resorces(Gold, Silver, Copper etc.).
And Fujiwara sholud not be a kind of sub-faction, I think at a moment now.

4.
I think it's good to use Emperial Guard Units(Martial Ministers) of Heian Kyo court.
They are not Samurais, but a few Officials of the court.
There would be 2 models of them. They were called as Sokutai(束帶).


So please let me know about present unit roster of Japanese faction.

[Yelü Dashi]

The only roster there is one we have in the preview, which is only four units:

Daikyu_Bushi
Naginata_Shinobe
Sword_Bushi
Yari_Shinobe

From what I read elsewhere Shinobe is the wrong term, it should be shimobe (下 部), who served by the side of government officials during Heian period (just before the start of the mod) they were sort of like police ? I know that foot soldiers weren't called Ashigaru in the 12th century.

This is what I posted elsewhere - is it accurate at all?

Spoiler Alert, click show to read: 

Why not start on a basic foot solider wearing Haramaki armour:






1 tosei-sode
2 gyoyo
3 kusazuri
4 moro-got
5 uwa-obi
6 kawazutsumi-no-tachi
7 koshi-gatana
8 samurai-eboshi
9 oshitsuke-no-ita
10 hitatare
11 hitatare-no-hakama
12 habaki
13 sune-ate
14 ashinaga
15 se-ita (okubyo-ita)
16 age-maki

Armour detail:

Spoiler Alert, click show to read: 

The Haramaki armor first started to appear in the 13th century, as a lower class armor for foot solder. Like the O-Yoroi and Do-Maru it became commonly used in the Genpei Wars. The Haramaki was constructed from small scales of leather or metal laced into plates with cord and lacquered although the plates were mostly larger then ones used in the O-Yoroi and the Do-Maru making it much cheaper and less time consuming to use. Then each plate where laced together to form the armor. As with the Do-Maru the weight was mainly on the shoulders but some carried some of the weight on the hips. The armor was also much more form fitting then the O-Yoroi and slightly more then the Do-Maru. It is easy to get the Do-Maru and the Haramaki confused due to the similar look, the easiest way to tell the difference is to find the opening in the armor. If it opens under the right arm it's a Do-Maru is it closes in the back it's a Haramaki. I believe that this change came about with the change in mindset at the end of the Genpi Wars and the emergence of the boshido code.

The other , more common, main form of armour for retainers/foot soldiers was domuru:




1 samurai-eboshi
2 moro-gote
3 yoroi-no-hitatare
4 koshigatana
5 naginata
6 sune-ate
7 midare-o
8 gyoyo
9 Oshitsuke-no-ita
10 kusazuri
11 habaki
12 hattoh-gutsu
13 yoroi-no-hitatare-no shimo
14 kuro-ito-mune-akaodoshi

If this armour rgith for period, do you now where we can find some better image of it ?

[Yelü Dashi]

Reading a bit more about Heian-kyo I found this:

Fires were a constant problem as the palace compound was constructed almost entirely of wood. The Daigokuden was reconstructed after fires in 876, 1068 and in 1156 despite its limited use. However, after the major fire of 1177 which destroyed much of the Greater Palace (Dairi, the Daigokuden was never again rebuilt. The Burakuin was destroyed by a fire in 1063 and was never rebuilt.As of 960, the Dairi was also repeatedly destroyed by fires, but it was systematically rebuilt and used as the official imperial residence until the late 12th century.[10] During periods of rebuilding the Dairi following fires, the emperors frequently had to stay at their secondary sato-dairi (里内裏?) palaces within the city. Often these secondary palaces were provided by the powerful Fujiwara family, which especially in the latter part of the Heian period exercised de facto control of politics by providing consorts to successive emperors. Thus the residences of the emperors' maternal grandparents started to usurp the residential role of the palace even before the end of the Heian period. The institution of rule by retired emperors or the insei system (院政, insei?) from 1086 further added to the declining importance of the palace as retired emperors exercised power from their own residential palaces inside and outside the city.


After a fire in 1177, the original palace complex was abandoned and emperors resided in smaller palaces (the former sato-dairi) within the city and villas outside of it. In 1227 a fire finally destroyed what remained of the Dairi, and the old Greater Palace went into complete disuse

So that large palace complex (Greate Palace) in the pictures we've posted, wouldn't have been there in 1180 AD - rather government used the "Shinden-zukuri" style mansions of the Inner Palace:

Spoiler Alert, click show to read: 

This is not the Inner Palace, but the style of buildings is much similar:

So it appears that the rather grand Tang-style buildings in Heian-kyo were either destroyed or disused, giving wat to the Sato-dairi style palaces (里内裏), I assume things would be similar for Kamakura.
What would a Japanese village look like at this time ?

[RollingWave]

very informative thread, great job

[tokimitsu]

As for Uinits, Shimobe and Yoroi(O Yoroi, Do Maru, Haramaki) Yelu mentioned, also weapons of that time.

1.
As for Unit Roster

Daikyu_Bushi
Naginata_Shinobe
Sword_Bushi
Yari_Shinobe

Is this the unit roster of Japanese factions? Only 4 units? Hmmm....
I have thought that there would be more hidden units which had not been introduced yet in mini preview.
So my intention was to check the existing whole unit roster and to correct some faults in it
It seems that there are no proper unit roster for Japanese factions now.

I asked you that "Can I help with Japanese factions?" 1 year ago, but no one didnt answer to me.
So I thought that all the research about Japanese factions was finished.
Please let me know about the reason why we neglected Japanese factions, and the research progress of Japanese factions,
because I will be able to provide proper informations to make Unit roster only when I know about the reason.

And how many Japanese Units do we need?
If I'm informed what to do, I will make new Japanese Unit Roster including Minamoto, Taira and Fujiwara rebel as long as I can

[tokimitsu]

2.
As for Shimobe(下部)

what I read elsewhere Shinobe is the wrong term, it should be shimobe (下部), who served by the side of government officials during Heian period (just before the start of the mod) they were sort of like police ? I know that foot soldiers weren't called Ashigaru in the 12th century.

Yelu, you're right. May I add something on what you mentioned?
As yelu said, Term of Ashigaru was not existed at time of AUH. About this, I mentioned in my post too.

Shimobe was the slaves or servants of Kebiishi(検非違使)
Kebiishi did the works of police, trials, impeachments of Heian Kyo during Heian period.
Kebiishi was high-ranked minister of Imperial court, so actual police works were performed by his servants, Shimobe, as you said.
But, in the 12th century, Kebishi lost their rights to keep public order, judge, impeach.
The reason is the collapse of Ritsuryo Taisei(律令体制 Constitution system) of ancient Japan.
Constitution system aimed centralized country by Japanese Emperor.
Kebiishi was one of public office of this Constitutional system.
But this system was failed and Kebiishi lost his rights and became the honorary office.
According to this situation, his servant, Shimobe(下部) began to disappear from the 11th century.
So in the 12th century, the term of "Shimobe" did not used commonly.

From the 11th century,
Samurais who had been originated from commonly armed local peasants began to take on police works of Heian Kyo
(This police works of Heian Kyo was called as "O-Ban-Yaku(大番役)" in Japanese")
These Peasants Samurais obey privately to big Samurai corps(Bushidan 武士団) which was organized by Minamoto and Taira clans.
This police work by Samurais made Bushidan to be influential to central court.
Passing by Hogen(保元) Disturbance (1156) and the Heiji(平治) Disturbance (1160), these Samurai corps became fatal to Emperor and his court, as you know.
The Peasants Samurais who obey privately to big Samurai corps was called as Roju(郎従) or Shoju(所従) or Roto(郎党).
These terms mean "Servant Group" of Bushidan(Samurai corps).
They were servants of the leader of each Samurai Corps. They were not obedient to Emperor and his court.
Bushidan was not official army of Japanese nation, but the private warriors who was under each clan leader's command.

So I suggest that it's good to use Roto, Shoju, Roju rather than Shimobe.

And I would like to use Sokutai(束帯) and Kebiishi(検非違使) as Japanese Imperial Units, which can be retrained only in Heian Kyo settlement.

[tokimitsu]

3.
As for Yoroi(鎧 Armor)

Nice research, Yelu.

Let's start with O-yoroi(大鎧), tha Archer Cavalry's Armor,
Because Domaru and Haramaki was developed from this O-yoroi(大鎧).
O-yoroi means "Big Armor" which high ranked Samurais put on.
High ranked Samurais are all Archer Cavalry at that time.
O-yoroi was fit to horse riding.

I will point out and make clear main features of O-Yoroi to help design the Diakyu(大弓) Archer Cavalry.
Please see this image I edited.

Spoiler Alert, click show to read: 

Area 1 in Green line is O-Sode(大袖) to protect upper arms and elbows.
They are wide & big sheets, and not fixed to upper arms. They are fixed only to shoulder.
So when Samurai raise his hands up, these O-Sodes droop down. (See Red circle area in 2nd image)
Area 2 in Blue line is called as Kusazuri(草摺) which protect thighs.
The main point is Kusazuri consists of 4 sheets(front-right-back-left).

So I would like to tell modeller to realize these features in unit design.

These images are Daikyu Archer Cavalry's full arm

Spoiler Alert, click show to read: 

Red circle 2 and 3 show the abundant shape of inner armor. Compare the slim shape of inner armor of red circle 1 with them.
Please reflect these differences into the Unit.

[tokimitsu]

4.
As for Yoroi 2

This is what I posted elsewhere - is it accurate at all?

Very nice research for Haramaki and Do-maru.
May I add some explainations on your research?

From 11th century, as Yelu said, Domaru(胴丸) and Haramaki(腹巻) have been co-existing as the foot soldiers' armor.
Because O-yoroi was monopolized by high ranked Samurais, and it was not fit for Infantry.
Domaru and Haramaki are more light and slim than O-yoroi, so they stick to wearer.
O-yoroi has 4 sheets of Kusazuris(草摺 protectors of thighs), But Domaru and Haramaki have many Kusazuris(草摺)
Generally Domaru has 8 sheets, Haramaki has 7 sheets of Kusazuri.

As Yelu said,

It is easy to get the Do-Maru and the Haramaki confused due to the similar look, the easiest way to tell the difference is to find the opening in the armor. If it opens under the right arm it's a Do-Maru is it closes in the back it's a Haramaki.

He pointed out sharply.
Domaru(胴丸) has its opening in its right side.
Haramaki(腹巻) has it in its back side.
For reference, O-yoroi has its opening in its left side.

These images Yelu quoted is about Haramaki. You can see the opening at its backside.

But this is Haramaki of Muromachi period(室町時代) in the 15th century.
So We can't use this model for AUH.
This style is mixture of Haramaki and Toseigusoku(当世具足 Sengoku periodi's style).
Do you see the added armor sheet on the backside opening in red circle?

And this backside armor sheet can be seen in red circle of the image below
(this armor is not same as the armor of the first 2 images though they are all Haramaki)
This armor is for the 14th century of Nambokucho period(南北朝 時代)



But in the 12~13th century, Haramaki didn't have its backside armor sheet.
Do you see backside of armor opened in red circle?

In Heian and Kamakura period, Haramaki didnot have its backside armor sheet, like the boy put on in image.

So, when modeller design Haramaki of the 12th~13th century, he should make the backside of Haramaki opened without backside armor sheet.



Yelu also quoted this Kamakura Samurai with Domaru.
We can use this unit for AUH mod.

As Yalu said, you can recognize that this is Domaru
because this armor in this image doesn't have its opening at its backside.

[Yelü Dashi]

Is this the unit roster of Japanese factions? Only 4 units? Hmmm....
I have thought that there would be more hidden units which had not been introduced yet in mini preview.
So my intention was to check the existing whole unit roster and to correct some faults in it
It seems that there are no proper unit roster for Japanese factions now.

I asked you that "Can I help with Japanese factions?" 1 year ago, but no one didnt answer to me.
So I thought that all the research about Japanese factions was finished.
Please let me know about the reason why we neglected Japanese factions, and the research progress of Japanese factions,
because I will be able to provide proper informations to make Unit roster only when I know about the reason.

And how many Japanese Units do we need?
If I'm informed what to do, I will make new Japanese Unit Roster including Minamoto, Taira and Fujiwara rebel as long as I can

I forgot the two Sohei units - one with armour, one without (all the pictures are in the preview). You should know better than to think we would hid any units or research from you . We are not like that, and I can only apologise if we ignored your suggestion, though I think we always said we would come back to Japan. It was the first faction we looked at, and the unit were made very quickly without a lot of thought (at that time it was only me and Chris). We admit we made some mistakes. If you're willing to develop their rosters properly we'd appreciate it, you can decide how many units - I would think 5-6 shared one, and 1-2 unique (not inlcuding sohei) but its up to you.

Many again toki, you're a huge asset at the moment.

EDIT: can't see the pictures in the last two post ?

[tokimitsu]

Wow Yelu have already posted reply. I appreciate you. I just wanna know how Japanese research progress. I didn't mean that I wonder If we AUH team hide some units or not. Just I thought there would be Japanese unit roster and researches I can't find somewhere in AUH dev forum so I asked you where it is. And I really admire Yelu and Augustus' researches. and I understand some mistakes because there are too many factions for Yelu and Augustus to research. Ok I clearly understand the situation.
As for 3rd and 4th post,it took long time to make these post because I'm using Korean-English dictionary when I write post. Please understand me, my English is poor. I will complete these posts when I type with my PC. I'm writing this post with my iPod touch. iPod touch is very uncomfortable to attach scripts with images. can't work with Photoshop either.

[Wundai]

Hah very nice, look at Toki's devotion to All Under Heaven, he even posts here with his IPod Touch I bow to you

[tokimitsu]

Thank you, Wundai

[tokimitsu]

5.
As for Weapons


In AUH period, Japanese only used 3 weapons

• Long Bow : called as Daikyu(大弓) or Yumi(弓)
• Naginata(長刀)
• Sword : called as Tachi(太刀). Used as subordinate weapon. This is not Katana.

Daikyu(long bow) was monopolized by high-ranked Samuris.
Missile range is 50m. Very short range because Daikyu was made of only a Bamboo.
Elastic power was insufficient to kill the enemies at a long distance.
So bow became longer and longer to enhance the elastic power, but there were limits for missile range to be over 50m.
Because of Japanese humid climates, they could not make compound bows like Korean compound bow.
Also in Japan, there are no yew tree, so Japanese could not make superb long bow like English long bow.
But main battle strategy was firing arrows among the high-ranked Samurais(almost of them are Archer Cavalry).
They avoided fighting closely.


But lower Samurais, who was Infantry, did fight closely. They used Naginata(長刀) to fight closely.
Naginata was very widely and commonly used by foot soldiers in Japanese medieval era.
But there were no Yari(槍 Spear, Pike) to pierce in AUH period.
Yari begin to appear in Sengoku period in 15th century.
Only Naginata at that time.

Spoiler Alert, click show to read: 

So Yari blade in circle 1 cannot be used for AUH, sorry to say. And also Naginata was not long as the Yari in this image, either.


As for Tachi(太刀)
This Samurai carry Tachi on his waist.
This Tachi is different from Katana. Katana was invented in 15th century.

The different points of Tachi are like these;

• Tachi was used as the secondary weapon of Samurais. Almost of them use Tachi only when they execute captivated enemies or kill stragglers. Lots of Samurais use their Tachis as ornaments. So you can hardly see Sword-wielding Samurai in battles of AUH period. In contrast, Katana was the main weapon of Sengoku period.
• Tachi has curved short handle. So Samurai scarcely use Tachi with his two hands. Curved handle needs only Samurais' one hand. But, Katana need to be wielded by two hands. Its handle is more straight and longer than that of Tachi.
• From Sengoku Jidai, Tachis disappear from the battlefields. They become decorations to show authority of Daimyo or Shogun. Tachi was replaced by Katana in battlefields.
• The tip of Tachi is more narrow than its blade. But Katana keep almost same width all through its blade.

I think this sword in the image below is similar to Katana rather than Tachi. Daito(大刀) didnot exist in AUH period.

Spoiler Alert, click show to read: 

Compare the 2nd image with the 1st one. The 1st image is Yari Samurai of Sengoku period.
You can see that how to carry Katana is opposite to that of Tachi. The back of Katana is upside down(in 1st red oval)
←Katana Tachi→
The Katana's method in the 1st image is more comfortable to pull out the Sword.
In the 1st image, Katana is fixed to Samurais body, but Tachi in the 2nd image is dingle-dangling from Samurai's waist.
To pull out the sword rapidly, fixed method like 1st image(Sengoku style) is more efficient.

Here are Tachi(太刀) of the 11~14th century.

Spoiler Alert, click show to read: 

I think Wundai, a Katana specialist, would know well about the differences.

So if I make Unit Roster, I will use these 3 items(Daikyu, Naginata, Tachi) for Japanese units.