The Republican triumphs in the November elections put the job of writing next year’s Senate defense policy bill in the hands of a leading critic of the Obama administration’s national security strategy and an aggressive watchdog over Pentagon weapons procurement policies.

With Arizona Republican John McCain in line to succeed retiring Michigan Democrat Carl Levin as Senate Armed Services chairman, the committee will probably produce a fiscal 2015 defense authorization bill that pushes the White House to be more assertive in the world’s hot spots, while also moving to overhaul the way the Pentagon buys its weapons.

McCain has accused the administration of moving too tentatively to challenge the Islamic State terror group, to arm moderate Syrian rebels and to provide weapons to Ukraine. The 2008 GOP presidential nominee has criticized the administration for withdrawing all U.S. troops from Iraq in 2011 and can be expected in his new role to scrutinize the planned drawdown of forces in Afghanistan by 2016, which McCain sees as squandering the security gains made in recent years.

Despite the Arizona Republican’s hawkish national security credentials, he is hardly a rubber stamp for the Pentagon. He’s unlikely to support deep cuts in military spending levels, but he can be expected to keep a close eye on weapons procurement.

The former Navy captain and Vietnam War prisoner of war will be working with ex-West Pointer and Army Ranger Jack Reed of Rhode Island, the committee’s senior Democrat. Reed, who voted against the Iraq War authorization in 2002 and has backed the planned drawdown of U.S. forces in Afghanistan, will serve as a foil for McCain — and a strong supporter for the White House — on operational issues.

On the House side, Armed Services Chairman Howard “Buck” McKeon of California is retiring and his likely successor is Texas Republican Mac Thornberry, who lost two earlier bids for the chairmanship.

Thornberry has focused on a range of issues, including ensuring the government has the necessary legal authorities to fill missions as varied as cybersecurity and detaining and prosecuting alleged terrorists.

Thornberry’s promotion is not guaranteed — Rep. J. Randy Forbes of Virginia, an ardent Navy champion, is expected to vie for the job. Both men are unabashed hawks, though the delicate work of drafting a bill that gets broad bipartisan support could come more naturally to Thornberry than Forbes, who tends to be a more politically polarizing figure on the committee.