By the time World War I began Mubarak closely sided with the British against the Ottomans, and the 1913 Convention was rendered null. In support of the war effort Mubarak sent a force to Umm Qasr, Safwan, Bubiyan, and Basra to expel the Ottomans in November 1914. In exchange the British government recognized Kuwait as an “independent government under British protection.” There is no report on the exact size and nature of Mubarak's attack, though Ottoman forces did retreat from those positions weeks later. Mubarak soon removed the Ottoman symbol that was on the Kuwaiti flag and replaced it with “Kuwait” written in Arabic script. Mubarak's participation and previous exploits in obstructing the completion of the Baghdad railway helped the British safeguard the Persian Gulf from providing Ottoman and German reinforcements.