In this manner, within five or six years after he was chosen king, Henry had accomplished his difficult task. Chiefly by peaceful means, by a combination of energy, patience and forbearance, he had subdued the elements of disorder in Germany, and united both princes and people under his rule. He was now called upon to encounter the Hungarians, who, in 924, again invaded both Northern and Southern Germany. The walled and fortified cities, such as Ratisbon, Augsburg and Constance, were safe from their attacks, but in the open field they were so powerful that Henry found himself unable to cope with them. His troops only dared to engage in skirmishes with the smaller roving bands, in one of which, by great good fortune, they captured one of the Hungarian chiefs, or princes. A large amount of treasure was offered for his ransom, but Henry refused it, and asked for a truce of nine years, instead. The Hungarians finally agreed to this, on condition that an annual tribute should be paid to them during the time. This was the bravest and wisest act of king Henry's life. He took upon himself the disgrace of the tribute, and then at once set about organizing his people and developing their strength. The truce of nine years was not too long for the work upon which he entered. He began by forcing the people to observe a stricter military discipline, by teaching his Saxon foot-soldiers to fight on horseback, and by strengthening the defences along his eastern frontier. Hamburg, Magdeburg and Halle were at this time the most eastern German towns, and beyond or between them, especially towards the south, there were no strong points which could resist invasion. Henry carefully surveyed the ground and began the erection of a series of fortified enclosures. Every ninth man of the district was called upon to serve as garrison-soldier, while the remaining eight cultivated the land. One-third of the harvests was stored in these fortresses, wherein, also, the people were required to hold their markets and their festivals. Thus Quedlinburg, Merseburg, Meissen and other towns soon arose within the fortified limits. From these achievements Henry is often called in German History, "the Founder of Cities." [Sidenote: 928.]