Esper: Embassy attack is part of 40 years of maligned behavior from Iran

10:29

Defense Secretary Mark Esper joins Andrea Mitchell to discuss the latest developments on the ground following the attack on the American embassy in Baghdad. He warned that the U.S. could "take preemptive action" if Iran prepares additional attacks, and tells Andrea that a wave of U.S. troops deployed to Iraq to provide additional security will remain there as long as necessary.