Democrat Senator Kirsten Gillibrand opposes giving General James Mattis a waiver to become Secretary of Defense. Gillibrand, who is a liberal who loves the Iran deal, hates that Trump nominated a Secretary of Defense who actually wants to keep the country safe from radical Islam.
Because Mattis has not been retired from the military for seven years, he will need a waiver from both houses of congress. The nation maintains the rule of civilian control of the military and makes it difficult for career soldiers to become SecDef. The only soldier to get a waiver was George Marshall, author of the Marshall plan, after Harry Truman nominated him.
With ISIS on the march, China and Russia saber rattling, and Iran talking about expanding its nuclear program, Mattis makes a great deal of sense for SecDef. That is exactly while Gillibrand and other Democrats will talk about their respect for him, but try their best to block him.