“Lion of Midnight” (that is, of the North). Also known as Gustav II and Gustav Adolph. King of Sweden, military reformer, statesman, and greatest general of the Thirty Years’ War (1618-1648). Gustavus was crowned at age 17 when his father, Karl IX, died prematurely in the midst of the bitter War of Kalmar with Denmark. Gustavus immediately proved a brilliant organizer, innovator, and diplomat. Later, he would prove an even more able battlefield commander: Napoleon actually compared him to Alexander. For the first 10 years of his reign he was preoccupied with consolidating Sweden’s territory against Danish and Polish encroachment. He negotiated a peace with Denmark that permitted Swedish goods and copper, largely carried on Dutch ships, to pass through the Baltic Sound, in exchange for payment of a burdensome indemnity. He ended Sweden’s wars with Poland and Muscovy temporarily so that he could modernize Sweden internally and militarily, largely on the Dutch model. He compromised with the Swedish nobility, agreeing to a constitutional Charter that promised to uphold Lutheranism as the state religion. He did all this in order to clear the way for Sweden’s rise as a Great Power in the north, but also because he was a sincere Lutheran: he led troops in singing hymns as they marched to war, ordered prayers twice daily by the whole army, and assigned pastors to every regiment. This blend of prayer and black powder made the Swedish army feared and respected. It also gave Swedish troops unusual discipline and character on the battlefield.

Key to Gustavus’ political success was his thoroughgoing reform of the Swedish military. He professionalized the army, changing it from a semifeudal levy whose formations consisted of ill-trained peasants recruited locally to a national force of well-trained regulars secured through conscription. He emphasized drill, military discipline, and volley fire by regiments freed from the old formation of infantry squares and reorganized instead into flexible linear formations. Most of these changes had been advanced already by Maurits of Nassau. Gustavus took the best Dutch innovations out of the waterlogged and canalized environment of the Netherlands to maximize their revolutionary battlefield potential on the broad plains of Poland and Russia. This made the Swedish Army one of the first and the finest standing armies of the era. This well-drilled and disciplined army, infused with a conjoined spirit of martial patriotism and fervent Protestantism, was uniquely able to shift from offense to defense with a speed and efficiency unmatched by any other army in Europe, or the world. Gustavus then elevated Sweden to the first rank of powers by taking his new model army, strategic vision, and advanced and well-drilled tactics to Germany, where he decisively intervened in the ‘Great War’ of the 17th century.


Gustavus understood the role of shock in combat and sought to maximize it by hauling genuine field artillery to the field of battle to support his infantry while it maneuvered, and in firefights, rather than having the big guns follow in a cumbersome siege train to be deployed mainly against fortifications or solely in static position in battle. This achievement of massed, mobile cannon fire was made possible by long experimentation with shortening and thinning the extremely heavy barrels of the cumbersome Murbräcker cannon that then dominated Swedish (and German) service. This reduced weight, cut back the number of horses or oxen (and fodder) required to move the guns, and thus greatly improved their mobility. While Gustavus’ experiment with ‘leather guns’ failed, he produced 4-pounder iron cannon that could be towed from place to place according to the dictates of battle. In 1629 he ordered a series of small caliber, short-range pieces cast. They were pulled by a pair of horses using a two-wheeled gun carriage and hence were capable of off-road maneuvers. Some pieces were so small (11.2- and 3-pounders, sometimes called ‘regiment guns’ or ‘regementsstycke’), they could be towed by a single horse or manhandled by a crew of two or three men. Several of these small cannon achieved rates of fire that exceeded the best rates of musketeers.

Swedish light pieces were supported by heavies, which Gustavus standardized at 6-, 12-, and 24-pound calibers. The heavy cannon traveled with the siege train, each piece hauled by large teams of draught animals, or he moved them by barge, marching the army alongside the guns along riverine routes. The light pieces always traveled ahead, along with his infantry and cavalry for quick deployment. Gustavus also refined and standardized gunpowder charges for each caliber of gun. Bagged powder in pre-measured cartridges improved rates of fire and increased accuracy. His main tactical innovation was to reorganize the heavies into batteries to concentrate fire at selected targets. This was a highly effective and then still novel battle tactic. His light pieces were deployed in front of his infantry lines to provide harassing fire. In sum, changes in size and weight and standardization of caliber and ammunition permitted Gustavus to deploy the first true field artillery of the gunpowder era. In the view of some historians, this feat represented nothing short of a military revolution. If it did, that was not universally recognized by contemporaries: after his death even the Swedish Army sometimes reverted to using larger guns that were best suited to the siege operations that dominated mid-17th-century war in Europe. It was not until the innovations of Frederick the Great, who studied and appreciated the Swedish example of the previous century, along with more frequent battles of encounter in the mid-18th century, that field artillery became standard in all modern armies.

Infantry and Cavalry

Gustavus reformed the infantry by increasing the proportion of musketeers to pikemen to two-to-one (with variations), so that more men in each formation were able to bring fire to bear on the enemy, giving each brigade – the main Swedish formation – greater punching power. He adopted wheel lock muskets that were smaller and lighter than the Spanish matchlock and did not require a forked rest, which made his musketeers more mobile. He shortened the pike to just 11 feet, making his pikemen just as light and maneuverable as the musketeers they protected and drilled with. Brigades were divided into three ‘squadrons’ of about 500 men each. More importantly, Gustavus reduced the ranks to six, so that interior and back ranks had clear fields of fire (after firing, the front ranks knelt), while at any given moment a brigade was confident that half its men (three back ranks) stood ready to repel an attack with muskets loaded. Gustavus developed new divisional tactics to overcome the solid and less mobile Spanish tercios. He shifted from dense infantry squares to linear formation, wherein three or four brigades formed a flexible, articulated and extended battle line. The thinner ranks of his line infantry gave the Swedish Army a tactical maneuverability denied to heavy squares. Gustavus placed his smaller iron cannon before the infantry, adding to firepower in attack or defense. When flanked, Swedish infantry quickly articulated their line to bring musket volleys and light (11.2-pounder) field artillery to bear on their tormentors. The cavalry was deployed more traditionally on the wings of the infantry, from where they might attack the enemy’s cavalry and exploit exposed enemy flanks or rear. But the weight of a Swedish attack came from the infantry. The mobile field guns raked the enemy square or line with canister, punching bloody gaps in the ranks. Then the infantry closed to about 40 yards to maximize the effect of their musket volleys. After firing two or three salvoes, at most, the front ranks charged with pikes level and muskets reversed and used as clubs. Through all this, the back three ranks stood ready to exploit a breakthrough or pivot to defend the brigade’s flanks, or to counterattack if arrayed in defense.

Gustavus modeled his cavalry on the superb Polish horse that was still dominant in East European warfare but largely unknown in Western Europe. He stripped armor from men and mounts and replaced the wheel lock pistol, used to such little effect in the caracole, with the saber. Horses were retrained to trot and gallop rather than cantor toward the enemy. In sum, as Michael Roberts has shown, Gustavus returned to cavalry shock and speed in place of firepower. This took advantage of a widely noted Swedish military ferocity and ability to pursue a defeated enemy, whereas other cavalry deployed in overly dainty and largely ineffectual columns to perform the caracole. In battle, the first obligation of Swedish horse was to block enemy cavalry from taking offensive action, and secondly to exploit gaps or exposed flanks or other opportunities created by the superior firepower of the Swedish infantry and artillery. In strategy and tactics Gustavus stressed preparation, deliberation, and an offensive spirit that sought always to carry war to the enemy. He was among the first to employ recognizably modern techniques of combined arms by coordinating attacks by mutually supporting infantry, artillery, and cavalry units. Similarly, he pioneered fire and movement, and reverted to and restored the ancient principle of concentration of force at a chosen point of local superiority on the field of battle. The changes Gustavus wrought stunned more staid and conservative enemies and set their armies and generals reeling. These reforms took many years to implement, however, even in the Swedish Army: more recent research than Roberts’ has shown that Swedish cavalry never entirely abandoned the caracole before the 1680s.

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