Sigismund would not hear of peace, but under the curious habit of that day, of conducting war on a sort of picnic system, he did extend the existing truce for five years. At its expiration, in 1621, active war began. Gustavus, with twenty-four thousand men, making Livonia his objective, landed at Riga, took the place, and from thence as a base, conducted his campaign.
Sigismund represented the Catholic element; Gustavus was the most prominent Protestant prince, and as such received many urgent petitions for help from the harassed Protestants of Germany. The eventual necessity of taking a share in the religious war was clearly foreseen by Sweden. With the advice and consent of the ministry and people, Gustavus reorganized the army and created a distinctly national force of eighty thousand men, and based its discipline and character on the most intelligent foundation. Sweden thus acquired the first modern regular military organization. Other nations, as a rule, whenever a war was imminent, raised troops from the crowds of soldiers of fortune, with whom all Europe swarmed, and discharged them after its expiration. The Swedish organization consisted of one-quarter regular troops for service out of the country, and three-quarters landwehr for the defence of the Fatherland and for filling gaps in the regulars. Recruitment was by districts on a well-settled plan of quotas. The troops in service and the militia were scrupulously drilled and taught, uniformed, well armed and fed, and regularly paid.
The Polish war lasted until 1629, the campaigns being annual, but varying in scope. Gustavus invariably took the offensive, and was habitually successful. He was always head and front of every movement, full of intelligence, activity, and courage, ran constantly great personal danger, and suffered from frequent wounds. No character of modern history exhibits the qualities of the ancient hero so distinctly as Gustavus Adolphus. Cautious and intelligent to a marked degree in his campaigns, he was in battle a very Alexander for audacity and chivalrous bearing. Always in the thickest of the fray, he led his men in person, and, despite the protests of his generals and suite, could never be restrained from exposing himself at the point of greatest importance. He was unwisely reckless of his own safety, though never losing for a moment his cool calculation or power to gauge the situation. His army partook his enthusiasm, as it shared his earnest religious feeling, and was devotedly attached to him as man and king.
In 1628, Wallenstein, the distinguished commander of the Imperial forces, had won great success in northern Germany, and had laid siege to Stralsund. The German Protestants again turned with piteous appeals to Gustavus. The king well knew that sooner or later Protestant Sweden must, in self-defence, enter the lists against the Catholic Empire, and threw a Swedish garrison into Stralsund, which, gallantly backed by the citizens, held the place against Wallenstein’s best efforts.
In the campaign of 1629, the Emperor sent an army to reënforce the Poles. This the more impelled Gustavus to actively embrace the Protestant cause. At the end of this campaign, Sigismund, largely under the influence of Richelieu, was prevailed on to agree to a six years’ truce. France could not openly join the Protestants in their struggle against the Catholic Emperor, but was glad to see Gustavus do so in order to check such success by Ferdinand as might disturb the balance of power.
This truce ended the Swedish-Polish wars, which had lasted eight years (1621–1629). The king had conducted six campaigns against Poland, and two against Denmark and Russia. These were to him what the Gallic campaigns were to Cæsar, a practical school of war, in which both he could learn his trade, and his army be disciplined and toughened. He had observed the practical working of his new army organization, and learned the weak points of the existing system of war. Comparison showed the advantages of his own conceptions. In the three remaining years of his life he moulded these into a new art, which pointed the way back to a system full of intellectual and moral force as well as more consonant with common Christian charity. The king, during this period, gleaned varied experience. He learned the habits of different leaders and armies, and how to adapt his own ways to theirs. His infantry underwent a good schooling. His cavalry he gradually improved by imitating the admirable Polish horsemen, and by adding discipline and ensemble to it. His artillery gave a good account of itself. Under Gustavus’ careful eye, every branch of the service during these campaigns grew in efficiency. Equipment, arms, rationing, medical attendance, drill and discipline, field-manœuvres, camp and garrison duty, reached a high grade of perfection. Each year added to the skill and self-poise of the Swedish forces. They were distinctly superior to any European army of the day.
Not only had Gustavus learned to know his generals and men, but these had gauged their king. There had arisen between them that mutual confidence, esteem, and affection which only great souls ever evoke and keep. And as there was no danger or labor of which Gustavus did not bear with them his equal part, so the Swedish army saw in its king a harbinger of victory, a sure protection in disaster. Gustavus’ own character, his bravery, religious ardor, honesty, and humanity infused itself into every soldier in the Swedish ranks.
Gustavus Adolphus was now in a position to afford efficient aid to the German Protestants. The efforts of the latter had been noble, but far from systematic, and they were fast being driven to the wall. The war had been marked by barbarities characteristic of religious struggles, and by the adoption of happy-go-lucky plans of campaign. Armies had moved into a province, not because it was strategically important, but because it was rich in plunder. Manœuvres were conducted without reference to base or communications. There was no aim beyond temporary expediency in any one’s movements. A fortress would arrest the march of an army, which would sit down before it without the remotest conception of whether its capture would have an effect on the general result. Lack of system was supplemented by religious fanaticism, which made everything redolent of atrocity. No general but was characterized by some fearful vice. Gustavus Adolphus was destined to change all this in a short two years.
As a soldier Gustavus is less noted for his battles than for the conduct, in 1630, 1631, and 1632, of a campaign on one broad, intelligent, far-seeing plan, from which he never swerved. This of itself was an entire novelty in this period of shallow operations. In lieu of detailing one of his manœuvres, I will give a hasty sketch of his entire plan of campaign in Germany. This was the first crisply strategic series of operations since the days of Cæsar.
It was clear that if the Emperor overcame the Protestants of Germany he would turn on Sweden. To await attack was the preference of the Swedish ministry. But Gustavus pointed out the advantages of an immediate offensive war in Germany. The struggle would be kept from Swedish territory. The Emperor would not gain so much headway as to lay Sweden open to an exhausting war. They owed a duty to their oppressed Protestant brethren. He convinced his people and gained their support. He took with him fifteen thousand men. This number he expected to, and did in fact, largely increase in Germany by recruitment and the aid of Protestant allies.