He was the second son Matthew Church, a Quaker merchant in the North Mall area of Cork, and Anne Dearman, originally from Braithwaith, Yorkshire. At the age of sixteen he ran away from home and enlisted in the British Army. For this violation of its principles he was disowned by the Society of Friends, but his father bought him a commission, dated 3 July 1800, in the 13th (Somersetshire) Light Infantry. He served in the demonstration against Ferrol, and in the expedition to Egypt under Sir Ralph Abercromby in 1801, where he took part in the Battle of Abukir and the taking of Alexandria. After the expulsion of the French from Egypt he returned home, but came back to the Mediterranean in 1805 among the troops sent to defend the island of Sicily. He accompanied the expedition which landed in Calabria, and fought a successful battle against the French at the Battle of Maida on 4 July 1806. Church was present on this occasion as captain of a recently raised company of Royal Corsican Rangers. His zeal attracted the notice of his superiors, and he had begun to show his capacity for managing and drilling foreign levies. His Corsicans formed part of the garrison of Capri from October 1806 till the island was taken by an expedition directed against it by Joachim Murat, in September 1808, at the very beginning of his reign as king of Naples. Church, who had distinguished himself in the defence, returned to Malta after the capitulation.