During the 1998–1999 Kosovo War, the Serbian Army made extensive use of deception, which caused NATO forces to expend time, effort, and resources attacking false targets. According to post-war assessments, NATO often attacked crude decoy tanks, artillery, and wheeled vehicles made of easy to obtain material including sticks and plastic. Many of these decoys included easily produced heat sources, such as burning cans of oil, which deceived the thermal imaging systems in NATO aircraft. As a result, NATO believed it inflicted far more damage on the Serbian Army than it actually had, and Serbia gained a propaganda victory by showing how easily NATO had been deceived.