A Vietnam veteran's epic poem of war

It's not often (if ever) a recipient of the Medal of Honor is also a published poet. But retired Green Beret John Duffy turned his trial-by-fire into an epic poem of the Vietnam War. 

It was a brutal battle; no quarter asked, none given. You killed the enemy or the enemy killed you.   

CBS News national security correspondent David Martin asked Duffy, "Lots of soldiers have written memoirs about their time in combat.  You chose to write poetry. Why?"