In World War II, the Western Allies used Iran as a conduit to transport military and industrial supply to the USSR, through a pathway known historically as the "Persian Corridor". Britain utilized the Persian Gulf as the entry point for the supply chain in order to make use of the Trans-Iranian Railway. The Persian Gulf therefore became a critical maritime path through which the Allies transported equipment to Soviet Union against the Nazi invasion. The piracy in the Persian Gulf was prevalent until the 19th century. Many of the most notable historical instances of piracy were perpetrated by the Al Qasimi tribe. This led to the British mounting the Persian Gulf campaign of 1819. The campaign led to the signing of the General Maritime Treaty of 1820 between the British and the Sheikhs of what was then known as the 'Pirate Coast'.