the Spanish Nationalist Air Force to transport Army of Africa troops from Spanish Morocco to the Spanish mainland at the beginning of the Spanish Civil War. Airlifts became practical during World War II as aircraft became large and sophisticated enough to handle large cargo demands. The Germans used an airlift in successful relief of the Demyansk Pocket, albeit with the Luftwaffe suffering considerable losses to its fleet of transport planes. Due to the apparent vindication of the airlift tactic, Chief of the Oberkommando der Luftwaffe Hermann Göring assured Adolf Hitler that the Luftwaffe could conduct an airlift on a larger scale, which was the key factor not to let the Sixth Army withdraw from Stalingrad after its encirclement by the Red Army. However the Luftwaffe was strained at this point while facing better prepared Soviet air forces at Stalingrad, so they were unable to delivery the necessary supplies before the airfields were overrun. In spite of the airlift's obvious shortcomings, Hitler refused permission for the Sixth Army to attempt a breakout, eventually leading its commander Friedrich Paulus to surrender. The U.S. Army Air Force's Air Transport Command began the largest and longest-sustained airlift of the war in May 1942, delivering more than half a million net tons of materiel from India to Free China over the Hump by November 1945. After many USAAF airmen were shot down in Nazi-occupied Serbia during Operation Tidal Wave, the U.S. Fifteenth Air Force and the Office of Strategic Services evacuated a number of them in Operation Halyard with the assistance of Draža Mihailović's Chetnik partisans. Additionally, at the end of World War II the USAAF and the RAF arranged humanitarian airdrops to the Nazi-occupied Netherlands through Operations Manna and Chowhound to alleviate the Dutch famine of 1944-45. The largest airlift was the Berlin airlift, lasting from June 1948 to September 1949, an international operation intended to thwart the blockading of West Berlin by the Soviet Union. The airlift was arranged by the U.S. Air Force, the British Royal Air Force, the French Air Force, the Royal Canadian Air Force, the Royal Australian Air Force, the Royal New Zealand Air Force, and the South African Air Force using C-47 Skytrains, C-54 Skymasters, Handley Page Haltons, and Short Sunderlands. Many Soviet and Western leaders alike initially assumed that an airlift to resupply West Berlin would fail because of the results of the Battle of Stalingrad. However,