 The British informed Spain of its intention to build barracks on the isthmus' neutral ground in 1815, which Spain agreed to for the duration of, and in order to assist in dealing with, a yellow fever epidemic in Gibraltar, and the buildings remained thereafter.The airport was built unilaterally by the British on another section of neutral ground in 1938, while Spain was fighting a civil war, thus further reducing the original size of the neutral ground.Referring to the current demarcation, Spanish official terminology always uses the word "fence" ("verja" in Spanish) instead of "frontier" or "border", since it does not acknowledge the possibility of having a frontier with what Spain considers to be its own territory.