The war song "Over There," written by George M. Cohan, gained popularity among the U.S. military and the American public during both World War I and World War II. 

Written shortly after the U.S. joined World War I, it acts as patriotic propaganda urging American men to enlist in the American Expeditionary Forces. 

It was not widely used during the Vietnam War, but gained some popularity again after the September 11 attacks and during the war on terror. 

Johnny, get your gun, get your gun, get your gun.
 Take it on the run, on the run, on the run.
 Hear them calling you and me,
 Every Son of Liberty.
 Hurry right away, no delay, go today.
 Make your daddy glad to have had such a lad.
 Tell your sweetheart not to pine,
 To be proud of her boys in line.
 
 Johnny, get your gun, get your gun, get your gun.
 Johnny, show the Hun you're a son of a gun.
 Hoist the flag and let her fly;
 Yankee Doodle, do or die.
 Pack your little kit, show your grit, do your bit.
 Yankee to the ranks from the towns and the tanks.
 Make your mother proud of you
 And the old red, white, and blue.
 
 Over there, over there,
 Send the word, send the word over there
 That the Yanks are coming, the Yanks are coming,
 The drums rum-tumming everywhere.
 So prepare, say a prayer,
 Send the word, send the word to beware –
 We'll be over, we're coming over,
 And we won't come back till it's over, over there.