Ming Dynasty two-handed swords (probably early to mid-17th century) known then as the "changdao" but are more popularly known today as the "Miao Dao". These blades have ridged cross-sections and were obviously inspired by the large Japanese swords (known as "nodachi") used by the Japanese pirates raiding the Chinese south-eastern coast. As for the diagrams showing the swordsmen, they are from a Ming martial arts manual published in 1621.
These large 2-handed sabers were first used by the Northern Border Troops under the command of Ming General Qi Jiguang in the late 1560s-70s to deal with Mongol cavalry, and remained in use right up to the late Ming (1620s-1644). At that time, these sabers had an overall specified length of 1.95 meters. General Qi, who lived from 1528-1587, had written the influential training manual "Lian Bing Shi Ji" while he was the commanding and training officer for several northern units bordering Mongolia. Commanding about 100,000 men, some of the best troops of the Ming empire, he had successfully deterred Mongol aggression at the border for over 10 years. The structural components he had setup to deal with the formidable Mongol cavalry armies were to consist of 4 parts:
1) Combat Wagon Force
2) Infantry Force
3) Cavalry Force
4) Baggage Supply Train
A brief description of General Qi's Commando Team:
The Combat Wagon Force and Baggage Supply Train are equipped with large and medium caliber cannons. The "Commando Team" is the non-artillery combat component of the Combat Wagon Force and uses a wagon as a large mobile armoured platform. It consists of 8 men -- 4 musketeers (soldiers armed with Chinese-made Portuguese-style matchlocks) individually equipped with the Miao Daos, 2 musketeers both equipped with shield and single-handed saber, and 2 more soldiers both equipped with trident polearms and fire-arrows (arrows driven by gunpowder-propelled rockets).
Upon contacting the enemy, the wagons are to be setup in a rectangular formation and all personnel are to withdraw within this defensive perimeter. After the cannons, muskets and fire-arrows are fired first at long range against the Mongols, the Commando Team would park their long range weapons inside the wagon, then move out of the defensive perimeter and deploy in formation, using their Miao Daos, sabers and shields, plus the trident polearms for close-quarters combat.
As mentioned earlier, the Combat Wagon Force and Baggage Supply Train are equipped with large and medium caliber cannons. General Qi stipulates that for non-artillery soldiers, almost all soldiers specifically equipped with the musket were to be issued with the Miao Dao as a standard issue close-quarters weapon.
The percentage of non-artillery soldiers in the Combat Wagon Force and Baggage Supply Train equipped with this musket/Miao Dao combo (ie those who are not manning the cannons) is 50%.
Another 50% of the Infantry Force are also equipped with the combo. As for the Cavalry Force, the muskets/Miao Dao takes up 20%.
One simple and specific training technique for General Qi's soldiers wielding the Miao Dao is to setup two thick wooden poles, one short and one long, spaced 2 feet apart.
The soldier will then use the Miao Dao like a zhanmadao, bending low while advancing and striking first at the bottom part of the shorter pole to simulate cutting through the horse's legs, afterwhich he will raise and turn slightly to strike the upper part of the longer pole, simulating the strike on the horse's head -- A practical scenario for when the horse dies, the enemy soldier/rider loses his mobility and becomes meat on the platter for the Chinese soldiers.
General Qi had also stipulated compulsory 2-person combat drills using wooden sticks for mock practice, for use in his army.
In my opinion, later on, the Ming "changdao" appears to have evolved into the "wodao" during the Qing Dynasty, as a 2-handed saber used by the Green Standard Army. See my webpage on "Illustrations of Qing Regulation Swords".
Click on the above pic to view other examples of Chinese sabers with ridged cross-sections.