A grenade sails out. One guy jumps on it and takes the blast and saves his three buddies. The answer matters. You'd feel cheated if it never happened. Without the grounding reality, it's just a trite bit of puffery, pure Hollywood, untrue in the way all such stories are untrue.
Absolute occurrence is irrelevant.
A grenade sails out. One guy jumps on it and takes the blast, but it's a killer grenade and everybody dies anyway. That's a true story that never happened.