Yorck left Prussia and joined the Swiss mercenaries in Dutch service in 1781. He took part in the operations of 1783-84 in the East Indies as captain at Regiment de Meuron. He also took part with the French army in a battle against British troops in Cape Town. Returning to Potsdam in 1786 he was, on the death of Frederick the Great, finally reinstated in his old service by the new king Frederick William II, from 1792 in the rank of major. In 1794/95 he participated in the operations in Poland during the Kościuszko Uprising, distinguishing himself especially at Szczekociny.