Kosice attack (26 June 1941) refers to a feign by Germany to provoke Hungary into attacking Russia in World War II. On 26 of June, 1941, four days after Hitler attacked the USSR, two unmarked planes sent by Germany attacked the Hungarian town of Kosice. At that time Hungary was Germany's ally. The Hungarian government erroneously assumed the planes were Soviet, and therefore declared war on the USSR on 27 June 1941, which is what Hitler wanted.
NOTE: present day, Kosice is part of Slovakia