As described in the book "World War II Aircraft in Combat," in early November 1944 the 15th Air Force was asked to provide close air support to Soviet forces chasing the Germans in Yugoslavia. P-38's of the 82nd Fighter Group operating from Foggia, IT were sent on the mission. The Soviets were so pleased with the P-38's effectiveness that they asked for the same support the next day. But the Soviets were now 100 km further than the day before and they were pressing the Germans so hard that the fleeing Germans and advancing Soviets were virtually one long line of vehicles. The P-38's hit the column and tore into the Soviets as well, killing a 3 star Soviet general officer. With no way to communicate with the Americans the Soviets called for help from their Yak-9's , which shot down two P-38's. The Americans then shot down four of the Yak-9's.