Secretary of State John Kerry appeared on "The Late Show with Stephen Colbert" Thursday night and discussed his involvement in the Iranian nuclear deal and how his experiences in Vietnam prepared him for his job.

Colbert grilled Kerry over the merits of the deal while Kerry defended the deal. Colbert also questioned him about Kerry comparing fighting in the Vietnam war with his determination to get the deal done.

"What's is the connection between the two of those," Colbert asked.

"War," Kerry answered. "If we didn't get an agreement with Iran, the pressures that would have mounted, because Iran was pursuing its (nuclear) programs."

Colbert then asked Kerry "so it was war or the deal?"

"Well our perception was it would not have been war on day one or immediately, but if Iran continued to enrich and Israel and other countries in the region saw them doing that, the pressure was going to mount to where you had to do something about it," Kerry said. "And if you tried negotiations and they failed or you can't negotiate, then you wind up being pressured toward conflict."

Check out the full interview with Kerry and Colbert below!