Germany went into the Second World War unable to import oil freely because of the threat of blockade, and it could not accumulate large stockpiles because of the cost. An essay on energy in the geopolitics of late capitalism says Germany therefore depended on petroleum synthesized from coal, domestic crude oil, and overland imports primarily from Romania.
German leaders expected a series of short campaigns to deliver Europe. The plan failed when Britain kept fighting and Germany was left responsible for Europe’s oil requirements while cut off from world markets. In June 1941 Germany invaded the Soviet Union to reach the Baku oil fields, a goal it never achieved. Fuel shortages contributed to the failure of Hitler’s 1942 offensive: panzer divisions in the Caucasus were sometimes halted for days while they waited for fuel. By 1944 the Allies had destroyed Germany’s synthetic fuel plants, which provided 92 percent of its aviation fuel.
The essay sets that wartime supply problem inside a longer argument that control of exploration, transport and sale of oil became a currency of power in the twentieth century, and that later conflicts and sanctions have continued to treat energy routes and exports as strategic leverage.