He was on the 2009 mission to rescue the captain of the merchant ship Maersk Alabama, who was taken hostage by Somali pirates. That episode was featured in the Tom Hanks movie "Captain Phillips."
And he was part of the group that helped retrieve Marcus Luttrell, the sole survivor of a four-man team attacked in 2005 while tracking a Taliban leader in Afghanistan. The Luttrell episode was featured in the 2013 film "Lone Survivor."
Long before those operations, O'Neill came to embody the dramatic transformation of the role of U.S. special operations over the last 13 years.
O'Neill joined the Navy in 1995, and in those pre-9/11 days, the SEALs did a lot of training with foreign militaries.