In 1190, some German merchants set up a field hospital at the siege of Acre. The hospital soon became an Augustinian monastery, then a military order like the Templars. It was called the Order of the Brothers of the German House of Saint Mary in Jerusalem, or for short, the Teutonic (German) Knights. By 1209, it was increasingly a fighting force rather than a hospital. In 1220, the order purchased a castle on the road to Jerusalem, called Montfort or (for German tongues) Starkenburg. Its ruin is now a tourist attraction in an Israeli nature preserve.
The other military orders, the Hospitalers and the Templars, were prospering too. At this time, when the Crusader States were small and weak, the knight orders were correspondingly huge and powerful. Much of the settling and “peacekeeping” of the Holy Land was carried out by these non-governmental orders, who reported directly to the Pope. During this period, the Hospitalers built Krak des Chevaliers into a massive fighting machine that was almost unconquerable.
All three received by will acres of farm and forest land that they didn’t directly live on or rule, but they collected profits from it. The Templars owned so much of France that they became an international banking house. They pioneered the use of a cheque, that is, a certified withdrawal order on paper that could be presented in Acre after money had been deposited in Paris (or anywhere). All of the orders began managing such large tracts of land and sums of money that they were in effect supra-national organizations, floating sovereign states.
In 1211, the Teutonic Knights offered their services to King Andrew of Hungary, who would soon lead the Fifth Crusade. He gave them a province in Transylvania, where they began settling other Germans. They were supposed to help defend the border of Hungary against the Turkic Cumans. But like the other military orders, the German Knights soon grew so rich and powerful that they lost interest in serving the King of Hungary. They asked to be placed directly under the Pope, like the other orders. In 1225, Hungary revoked their land grant, though they did not carry out ethnic cleansing against unarmed Germans.
The Knights also offered to help defend the borders of Poland from the pagan Prussians. In 1226, Emperor Frederick II gave them a land grant to possess and rule any Prussian territory they could conquer. So they set out to do that. It took about 50 years, but they subdued it, both killing and baptizing as they went. By the early 1300s, there were Teutonic Order castles all over Poland, Lithuania, Estonia, Latvia, and Germany.
In 1230, the Knights declared a new Crusader State in central Europe, later governed from their main Marienburg Castle in Malbork, Poland. It was made of red brick, and it is the largest castle in the world. It’s now a museum, World Heritage Site, and so on.
And of course, the Teutonic Knights also fought in the Fifth Crusade, alongside the other orders. All wore large crosses, but the German knights wore black cross on white, while the Templars wore red cross on white, and the Hospitalers white cross on black.