tree of liberty

"Tonight I heard Brig. Gen. Hertling of 7th ATC say something I won't soon forget: Our soldiers have not lost their lives in Iraq; they have sacrificed their lives for freedom and for their brothers and sisters in arms. That struck me. Their lives were not lost or taken, but instead they have given their lives for something much bigger than themselves. That's a wise statement and a comforting way of looking at the situation. The enemy cannot take that which we have sworn to give so that the tree of liberty may be refreshed."
trying to grok