Some veterans bear visible signs of their service: a missing limb, a jagged scar, a certain look in the eye.
Others may carry the evidence inside them: a pin holding a bone together, a piece of shrapnel in the leg - or perhaps another sort of inner steel: the soul's ally forged in the refinery of adversity.
Except in parades, however, the men and women who have kept America safe wear no badge or emblem.
You can't tell a vet just by looking.
He is the cop on the beat who spent six months in Saudi Arabia sweating two gallons a day making sure the armored personnel carriers didn't run out of fuel.
She - or he - is the nurse who fought against futility and went to sleep sobbing every night for two solid years in Da Nang.
He is the POW who went away one person and came back another - or didn't come back AT ALL.
He is the Quantico drill instructor who has never seen combat - but has saved countless lives by turning slouchy, no-account rednecks and gang members into Marines, and teaching them to watch each other's backs.
He is the parade - riding Legionnaire who pins on his ribbons and medals with a prosthetic hand.
He is the old guy bagging groceries at the supermarket - palsied now and aggravatingly slow - who helped liberate a Nazi death camp and who wishes all day long that his wife were still alive to hold him when the nightmares come.
He is an ordinary and yet an extraordinary human being - a person who offered some of his life's most vital years in the service of his country, and who sacrificed his ambitions so others would not have to sacrifice theirs.
He is a soldier and a savior and a sword against the darkness, and he is nothing more than the finest, greatest testimony on behalf of the finest, greatest nation ever known.
So remember, each time you see someone who has served our country, just lean over and say Thank You. That's all most people need, and in most cases it will mean more than any medals they could have been awarded or were awarded.
Two little words that mean a lot, "THANK YOU".
Father Denis Edward O'Brien/USMC