Sweden indeed had a standing army by the mid 1620s, but its population was about an eighth of the Polish-Lithuanian Commonwealth in 1620 (1.25 million people in Sweden, over 10 million in the latter). Among other things,
Gustavus gave war a new look by not altering the tactical doctrine any arm (or even two), but by synthesizing existing practices, improving upon them (
Mauritz van Nassau and
Henri IV, for example), and forging a nationally conscripted army of combined arms, and drilled with precision under his assiduous guidance. Whether his 'new' cuirassiers galloped or sped at a trot (they perhaps galloped then trotted upon impact, as formation is more easily maintained at a trot), they achieved success when charging home, firing their pistols in a tight formation with cold steel, supported by infantry fire. In essence, they were often an effective battering ram assaulting an already softened foe from supporting firepower. Swedish discipline became exemplary, religious duties strictly observed, and crime virtually non-existent. Gustavus Adolphus' actions during his involvement of the Thirty Years War greatly influenced the political and religious balance of power in most of Europe at this time.
Before 1626, Gustavus' army was still basically, as he put it,
"My troops are poor Swedish and Finnish peasant followers, it's true, rude and ill-dressed; but they smile hard and they shall soon have better clothes."
Gustavus' army became a paradigm of one element from the classic military Byzantine manual, the Strategikon, written, according to tradition, by the emperor-general Flavius Maurikios Tiberius,
"Constant drill is of the greatest value to the soldier."
Gustavus formed military tactics centered around increased firepower, including mobile field artillery. His army was in peak form by 1631, and his system of cavalry charges, influenced by the Poles, initiated with pistol fire, integrated with infantry (pike and shot) and field artillery, supporting each other in self-sustaining combat groups, was the first time this had ever been seen in modern warfare. Much like Philip II of Macedon and Chinggis Khan in their day, Gustavus was arguably the greatest developer of a balanced army for his time. But perhaps more than any other great commander of history, his reforms touched on every area of military science, including the administrative and logistic branches.
But a topic of Gustavus' reforms must include the influence impressed upon him by the great Maurice of Nassau: the brilliant Dutch innovator and his staff created a military system of drill to train officers and soldiers, and began to move away from the dense column of the omnipotent tercio, developing a more extended and elastic formation. He equipped his cavalry with pistols and began to concentrate artillery pieces in batteries. Moreover, Maurice put supply, training, and pay on a regular basis. The tercio, an innovation for its time, was restructured to be smaller after the Battle of Rocroi in 1643, in which the stout tercios were blasted away by the maneuverability and superior firepower of Louis II de Bourbon (the Great Conde). But it was Maurice at Nieuwpoort (1600), then Gustavus at Breitenfeld (1631), who presaged that doom. Basically, Gustavus refined what Maurice did to a broader scale.
But things take time, and not without trial and error; Amrogio Spinola, another brilliant leader of this age, reversed this innovative trend for a while against the Dutch, and the Swedes, sans Gustavus, suffered a defeat at Nordlingen in 1634 against an army with the Spanish tercio on hand. But Johan Baner won victories thereafter.
The Swedish disasters at the hands of the Poles/Lithuanians at Kircholm (modern Salaspils, about twelve miles SE of Riga) and Klushino (Kluszyn) were in the past, and Gustavus would not let that happen again; no Swedish force would ever again be fooled by a feint to pull them out of a strong position (at least under him); his earthworks were not to 'hide' behind, in my opinion, but to provide security to fall back on if things went awry. This was sound war-making. It is opined by some that he waltzed into the Polish-Lithuanian Commonwealth while their backs were turned, and easily captured towns to set up his entrenchments. But I am inclined to think the Baltic ports of Pilawa (Pilau) and Konigsberg (modern Kaliningrad) could not have been vulnerable to the degree it was child's play for the Swedes to take them, and there was also much diplomacy involved. They probably were defended by the trace italienne system. The town of Zamosc, for example, though further to the SE, saw the construction of new walls and seven bastions by 1602. But it seems quite accurate the Swedish onslaught in the 1620s initially made good progress because of an overall vulnerable scenario of the enemy.
Dr. Geoffrey Parker, an expert on the Thirty Years War, wrote in his The Military Revolution, Pg 37,
"...Several outraged books and pamphlets were promptly written by Polish propagandists, excoriating the invaders for their 'unchivalrous deceit' in raising ramparts around their camps 'as though they needed a grave-digger's courage to conceal themselves', and deploring their painstaking siege techniques as 'Kreta robota (mole's work)'. But, mole's work or not, Crown Prince Wladislaw was immediately dispatched to the Netherlands to learn about these deceitful tactics at first hand. he was followed by Polish engineers, such as Adam Freitag who, in 1631, published at Leiden an international classic on developments in military fortification..."
This is from Richard Brzezinski, an authority on this chapter of history, who wrote a book on the Polish Hussars (possible red flag: Osprey Publishing),
"...if you take an UNBIASED (as in non-patriotic) view of Polish-Swedish actions from 1622 onwards through to the Great Northern War they are characterised by a consistent reluctance of the Poles to charge when the Swedish cavalry is deployed in formal battle-order backed by their infantry and artillery firepower. Take away the fire support, and the hussars are far less hesistant, and generally victorious..."
That may not be completely true, as some husaria did penetrate Swedish musketry formations at the battle of Mitawa (Mitau, modern Jelgava) in 1622, and again at Gorzno (Gurzno) in 1629 - but only initially; the threats were quickly closed. Excellent details are provided by experts on Zagloba's Tavern. Radoslaw Sikora, who denounces Brzezinski, and is a prime source for this topic, is working to right what he thinks are wrongs etc. He provides figures from the Polish army register, and Daniel Staberg, the Swedish expert, gives figures from some battle draws by Gustavus himself. But Sikora writes something peculiar, on the topic of the Polish husaria fighting Swedish regiments of musketeers,
"...Unfortunately I noticed that this selective and partial treatment of primary sources appear in Richard Brzezinski's work quite often. It is most apparent in the quoted descriptions of the hussaria fighting against the Swedish army (Kokenhausen, Mitawa/Mitau or Tczew/Dirschau). Anyone who knows what truly happened there grabs his head when reading how these battles are used to support false thesis of alleged considerable efficiency of firearms of the Swedish cavalry against the husaria."
What truly happened? Well, I feel one can admire something without it being a vice of 'partiality'. The battle of Mitawa was fought before Gustavus' efficient reforms took significant effect. Poland ultimately lost this war (I would say more on a political than military scale), and the husaria never defeated Gustavus (his tactical rebuff at Trzciana, in which he counter-attacked twice to protect his infantry, notwithstanding). Koknese was a Swedish victory, and Gustavus clearly overcame the husaria at Gniew (Mewe) and Tczew (Dirschau), via method. Sikora's opinion as to why the Sejm (Polish diet) acquiesced to favorable terms for Sweden in 1629, if they were not losing the military aspect of this war (as some Polish apologists believe) - one in which he compares the feeling of the people of the Polish-Lithuanian Commonwealth to that of the American people in regards to Vietnam (late 1960s/early 1970s) is incredulous. Perhaps I am misconstruing him, but Polish soldiers were fighting in their own land against an invader. I am the last poster who wishes to insult people, and Mr. Sikora, clearly a civil and intelligent man, is invaluable for providing much trivia for this period.
[b]From a political standpoint, the death of
Gustavus amid the fog at Lutzen, a month before his 38th birthday, was a disaster. Looking back, perhaps we can blame him for that element of his leadership of heroic self-indulgence, and he was getting a little impetuous, it seems. But his death might have removed the one man who seemingly was capable of imposing an end to the fighting. But that must be based on private convictions over any solid evidence; he may have come too late. Instead, the Thirty Years War dragged on for sixteen more years, witnessing hellish circumstances of disorganized and impoverished conditions. As the Dutch philosopher
Hugo Grotius, who paid much attention to the concept of 'humane' warfare, tells us,
"...I saw prevailing throughout Europe a licence in making war of which even barbarous nations would have been ashamed..."