Major military developments took place during the Thirty Years War – possibly more so than for many centuries before hand. Historians still debate whether a “military revolution” took place during the Thirty Years War, but what cannot be denied is the impact these military developments had and were to have over the next centuries.

The Thirty Years War saw a change from ‘little wars’ to what was effectively total war. A nation’s economy was based around fighting in the war and sustaining that nation’s position within the Thirty Years War. Civilian populations were adversely affected in a way not seen before. The size of armies grew massively – as did the cost of keeping those armies in the field. Armies themselves saw the first smattering of what could be called “professionalism” in the approach of Gustavus Adolphus.

The size of armies grew to sizes not seen before and they became more than a mere nuisance to the civilian population of Europe. These was made worse for the civilians in that armies tried to live off the land in an effort to reduce the cost of maintaining themselves – if that meant taking livestock and grain from civilians, there so be it. In an area where armies were temporarily based, they could decimate the land before moving on – though areas just 10 miles from a battleground or from where an army was based could be unaffected by an invading army.

Size of armies Spain Holland France England Sweden
1470’s 20,000 40,000 25,000
1550’s 150,000 50,000 20,000
1590’s 200,000 20,000 80,000 30,000 15,000
1630’s 300,000 50,000 150,000 45,000
1650’s 100,000 100,000 70,000 70,000

 As armies grew in size, control of them became more problematic. The biggest problem faced by commanders was communication between sections of an army while it was on the move. Successful armies, such as the Swedes under Gustavus, used smaller units of highly trained men within the army as a whole. A great deal of emphasis was put on the use of cavalry.

The most common tactic used was the caracole – a combined cavalry charge assisted by firearms. Eventually this was replaced by a full scale cavalry charge. Such tactics needed well trained and disciplined troops. The Thirty Years War saw the development of professionalism within certain armies such as the Swedes. Successful attacks were sustained and offensive tactics became the norm leaving soldiers little time to pillage as had happened in previous centuries. Those armies that still had such an approach to warfare proved unsuccessful in this war. A quick offensive campaign gave the enemy little time to prepare its defences. Therefore, the Thirty Years War saw a move to campaigns based on professionalism, speed and offensive in nature. Gustavus ensured that his men were regularly paid and that locals were treated well. If Swedish soldiers needed local produce they had to pay for it rather than simply stealing it as had happened all too often in the past.

Maurice of Orange is given a lot of credit for starting these reforms as is Gustavus Adolphus of Sweden.

“He (Gustavus) had a wider strategic vision; he took Maurice’s methods, added to them and improved them, and in so doing was to impose upon the art of war a pattern which it retained almost unmodified until the advent of the revolutionary armies of France.” (Roberts)

 Many military developments had also been learned during the Spanish-Dutch war. Great advances had been made in fortress warfare and the use of pioneers. But when the conflict restarted in 1621, few new innovations were hit upon. However, one development was the use of fewer ranks of soldiers making them less susceptible to artillery fire. Infantry had traditionally been held in the following formation


This kept the men in units that were easier to command as they were less spread out but an accurate artillery/mortar shell on such a formation would be disastrous. A side-on cavalry charge could also inflict great damage as the target was that much larger. The move went to


Though more difficult to command, this formation had greater protection against artillery fire. It was also a smaller target for a side-on cavalry attack. Any such attack in the rear of the formation could also lead to the attacking cavalry being engulfed by those not directly in line of attack. However, the success, or not, of such a formation depended on training and discipline.

The war also saw an improvement in firearms – though this was not restricted to just one side. The muzzle-loading rifle came in. War put emphasis on development and armies had better standardisation in weapon design. Maps and field glasses were more commonly used and most troops got paid on a regular basis. Training manuals became more widely used especially those by Jacob de Gheyn and Jacob von Wallausen.

The impact of Gustavus should not be underestimated.

He intensified the fire power of his army by reforming formations and introducing lighter weapons. He also introduced lighter artillery which made it a lot more mobile and fitted in with Gustavus’s belief that armies should be offensive and ready to move at a moments notice and carry the necessary clout to defeat the enemy. Being able to hit your enemy hard should not compromise your mobility. Gustavus also encouraged his officers to be more self-reliant on their own command abilities. Time could only be wasted if an officer had to report back to a senior officer for permission to do something. Delay also compromised speed of action. An army waiting for orders was an army almost certainly idle.

Gustavus also had to rely on mercenaries. The population of Sweden did not allow for a large army. At the Battle of Breitenfeld, only 20% of the Swede’s army was made up of Swedes. At the Battle of Lutzen, the figure was 18%. Mercenaries by their very nature were not reliable and they held money as their master. Mercenaries swopping sides in the lead up to a battle after being offered more money was not uncommon. The economic plight of Sweden after 1632, saw large numbers of mercenaries desert Sweden for better paid employment elsewhere.

The reforms of Gustavus also had their failures. After his death, the senior generals in the Swedish army did away with smaller artillery guns in favour of larger ones. Smaller guns may have been more mobile but the impact of a large artillery gun was far greater especially in siege warfare.

Towards the end of the war, armies got smaller. The sheer cost of keeping big armies in the field was beyond the economies of some nations. In 1631, Wallenstein had over 54 foot regiments and 75 cavalry regiments – over 100,000 men in all. However, military historians have concluded that this army was in fact 230,000 as it needed the extra 130,000 to keep 100,000 soldiers in the field. The 75 cavalry regiments would have needed a large number of blacksmiths alone to keep the horses shod.

 Wallenstein also agreed to raise an army but not to pay for it – this the Emperor Ferdinand had to do. The cost of the Thirty Years War for the Imperial treasury has been estimated at 250 million gulden. Spain’s contribution to her Habsburg’s cousin was a mere 1.9 million gulden while the pope, who saw the Emperor as the defender of Catholicism, provided just 900,000 gulden. Therefore, the people of the Holy Roman Empire had to foot the bill. One of the major developments of the Thirty Years War was the sheer cost of warfare itself and the implications this would have on nations within Europe.

Was there a military revolution in the Thirty Years War? Historians still disagree on this. The growth in the size of armies, the use of new weapons, the development of professionalism and new tactics have pushed some into deciding that there was a revolution at a military level. The counter-argument to this is the fact that no single army or combination of armies had the ability to deliver a knockout blow that lead to victory. The Peace of Westphalia is also known as the Peace of Exhaustion – all sides in the war were exhausted by the mid-1640’s. Limm believes that armies were capable of fighting a series of ad hoc campaigns but of not being able to defeat the other side to such an extent that it had to surrender.