 All the early references to its usage in the Oxford English Dictionary are to German fortifications.However, in the Far East the term was also applied to the earth and log positions built by the Japanese, the term appearing in a 1943 instruction manual issued by the British Indian Army and quickly gaining wide currency.By 1947 the word was familiar enough in English that Hugh Trevor-Roper in "The Last Days of Hitler" was describing Hitler's underground complex near the Reich Chancellery as "Hitler's own bunker" without quotes around the word bunker.