OGPU is a worldwide terrorist organisation. No-one knows what the letters stand for.
OGPU was formed in 1914, presumably by the Germans. Their original aim was to wreck British coastal strongholds, hijack merchant ships, and generally cause chaos. Following the 1918 truce, the German Navy decided to shut OGPU down, however several members (including Rankin) escaped from the docks in Murmansk and went on the lam, and eventually made their way to America, with the help of Johnny Cuba. One of their founders, The Mad Speedboat, was smashed by Warrior, and as a result, they declared war on all tugs. Ironically, most of OGPU's members are tugs themselves.
OGPU's whereabouts are currently unknown, however, it is believed that most of its members are quartered on America's East Coast, in the region of both Bigg City and Ggibs City. The Germans have recently begun a search for OGPU, with Hitler leading the hunt.