Ideally, it's a man with enough good qualities that he becomes a sort of standard by which to judge masculinity. The problems of such a thing ought to be apparent. More commonly, it's an example of an average human being (completely gender neutral) with a range of flaws and virtues wholly unremarkable and within a few deviations from the mean upon which a whole host of mythmaking is foisted.
I am the Infantry. I am my country’s strength in war, her deterrent in peace. I am the heart of the fight… wherever, whenever. I carry America’s faith and honor against her enemies. I am the Queen of Battle. I am what my country expects me to be, the best trained Soldier in the world. In the race for victory, I am swift, determined, and courageous, armed with a fierce will to win. Never will I fail my country’s trust. Always I fight on…through the foe, to the objective, to triumph overall. If necessary, I will fight to my death. By my steadfast courage, I have won more than 200 years of freedom. I yield not to weakness, to hunger, to cowardice, to fatigue, to superior odds, For I am mentally tough, physically strong, and morally straight. I forsake not, my country, my mission, my comrades, my sacred duty. I am relentless. I am always there, now and forever. I AM THE INFANTRY! FOLLOW ME!