The order formed at the end of the 12th century in Acre in Palestine. During the Middle Ages they were a crusading military order and wore white surcoats with a black cross. Once established in Prussia (Pomerania), the Order became involved in campaigns against its neighbours, the Kingdom of Poland, the Grand Duchy of Lithuania, and the Novgorod Republic. As well as their feudal levies the Order had a strong urban economy, hired many mercenaries, and became a naval power in the Baltic Sea.