The Teutonic Order is a Catholic religious order originally founded as a military order in the 12th century (c. 1190) in Acre.
The order was formed to aid Christians on their pilgrimages to the Holy Land and to establish hospitals. Its members have commonly been known as the Teutonic Knights, having a small voluntary and mercenary military membership, serving as a crusading military order for protection of Christians in the Holy Land and the Baltics during the Middle Ages.
In 1230, following the Golden Bull of Rimini, Grand Master Hermann von Salza and Duke Konrad I of Masovia launched the Prussian Crusade, a joint invasion of Prussia intended to Christianize the Baltic Old Prussians. The Knights had quickly taken steps against their Polish hosts and with the Holy Roman Emperor's support, had changed the status of Chełmno Land (also Ziemia Chelminska or Kulmerland), where they were invited by the Polish prince, into their own property. Starting from there, the Order created the independent Monastic State of the Teutonic Knights, adding continuously the conquered Prussians' territory, and subsequently conquered Livonia. Over time, the kings of Poland denounced the Order of holding lands rightfully theirs, specifically Chełmno Land and Polish lands that would be conquered later, such as Pomerelia (also Pomorze Gdańskie or Pomerania), Kujawy, and Dobrzyń Land.
The Order theoretically lost its main purpose in Europe with the Christianization of Lithuania. However, it initiated numerous campaigns against its Christian neighbours, the Kingdom of Poland, the Grand Duchy of Lithuania, and the Novgorod Republic (after assimilating the Livonian Order). The Teutonic Knights had a strong economic base, and so hired mercenaries from throughout Europe to augment their feudal levies, and became a naval power in the Baltic Sea. In 1410, a Polish-Lithuanian army decisively defeated the Order and broke its military power at the Battle of Grunwald (Tannenberg). However, the capital of the Teutonic Knights was successfully defended in the following Siege of Marienburg and the Order was saved from collapse.
In 1515, Holy Roman Emperor Maximilian I made a marriage alliance with Sigismund I of Poland-Lithuania. Thereafter, the empire did not support the Order against Poland. In 1525, Grand Master Albert of Brandenburg resigned and converted to Lutheranism, becoming Duke of Prussia as a vassal of Poland. Soon after, the Order lost Livonia and its holdings in the Protestant areas of Germany. The Order did keep its considerable holdings in Catholic areas of Germany until 1809, when Napoleon Bonaparte ordered its dissolution and the Order lost its last secular holdings.
However, the Order continued to exist as a charitable and ceremonial body. It was outlawed by Adolf Hitler in 1938, but re-established in 1945. Today it operates primarily with charitable aims in Central Europe.
The Knights wore white surcoats with a black cross. A cross pattée was sometimes used as their coat of arms; this image was later used for military decoration and insignia by the Kingdom of Prussia and Germany as the Iron Cross and Pour le Mérite. The motto of the Order was: "Helfen, Wehren, Heilen" ("Help, Defend, Heal").