President Barack Obama is nominating former Sen. Chuck Hagel (R-Neb.) as the next defense secretary and White House Homeland Security and Counterterrorism Adviser John Brennan as the next CIA director.

The battle lines over Hagel’s nomination are already being drawn, as at least two no votes from senators were registered before Obama’s pick was official.

If approved, Hagel, a Vietnam War veteran, would be the first enlisted soldier to ever assume the role of the Pentagon’s top civilian. Since leaving the Senate, Hagel has served on the president’s Intelligence Advisory Board and the Defense Policy Board. He is also currently the chairman of the Atlantic Council.

In nominating Hagel, Obama highlighted that experience, along with the former senator’s ability to function outside the fray of politics. As a Republican senator, Hagel bucked his party by opposing both the war in Iraq and the surge in Afghanistan.

“My frame of reference is geared toward the guy at the bottom who’s doing the fighting and the dying,” Obama says. “Our troops will always know that Secretary Hagel will be there for you.”

Now the action will move to the Senate, where Hagel’s confirmation is not assured. But the nomination did receive a signal of confidence from a key member of the Senate, Carl Levin (D-Mich.), chairman of the Senate Armed Services Committee (SASC).

“Senator Hagel is well qualified to serve as secretary of defense with his broad experience in national security affairs,” Levin says. “The Armed Services Committee will give prompt and careful consideration to Senator Hagel’s nomination for this critical position.”

But top Republicans on the committee are preparing for an aggressive confirmation process, particularly given Hagel’s comments about a “Jewish lobby” he has described as “intimidating” lawmakers, and support for negotiating with Hamas.

House Majority Leader Eric Cantor (R-Va.) may not be able to vote against Hagel’s nomination, but he characterizes Hagel’s views on Israel as “incendiary.” Cantor says, “Sen. Chuck Hagel is the wrong man for the job at such a pivotal time.”