According to one story , German intelligence found the phrase on captured American equipment . This led Adolf Hitler to believe that Kilroy could be the name or codename of a high-level Allied spy . At the time of the Potsdam Conference in 1945 , it was rumored that Stalin found " Kilroy was here " written in the VIP bathroom , prompting him to ask his aides who Kilroy was . War photographer Robert Capa noted a use of the phrase at Bastogne in December 1944 : " On the black , charred walls of an abandoned barn , scrawled in white chalk , was the legend of McAuliffe 's GIs : KILROY WAS STUCK HERE . " '' Digger History , the Unofficial history of the Australian & New Zealand Armed Services '' , says of Foo that " He was chalked on the side of railway carriages , appeared in probably every camp that the 1st AIF World War I served in and generally made his presence felt " . If this is the case , then " Foo was here " predates the American version of World War II , " Kilroy was here " , by about 25 years . . " Foo " was thought of as a gremlin by the Royal Australian Air Force , It has been claimed that Foo came from the acronym for Forward Observation Officer
Potsdam Conference
Potsdam Conference
Kilroy was here