salient

(military) An outwardly projecting part of a fortification, trench system, or line of defense.

1919, “General Pershing's Story”, in Americans Defending Democracy: Our Soldiers' Own Stories, World's War Stories, Inc., page 9:

On April 26 the First Division had gone into the line in the Montdidier salient on the Picardy battlefront.

1978, Jan Morris, chapter 9, in Farewell the Trumpets, New York: Harcourt Brace Jovanovich, page 193:

The battlefronts were often no more than a few hundred yards wide, and the salients never more than a few miles deep.

(geography) An elongated protrusion of a geopolitical entity, such as a subnational entity or a sovereign state.