With Congress back in town, the full-scale defense of the Pentagon’s budget is in full swing, with Republican lawmakers – and even, way off in Texas, former defense secretary Robert Gates – warning that the military shouldn’t be forced to make cuts beyond the $400 billion in savings planned over the next 12 years.

This week, Republicans on the House Armed Services Committee released a video, replete with footage from the attacks of Sept. 11, 2001, to make the case that further cuts would endanger national security. (See video above.) This morning, at a committee hearing featuring testimony from former chairmen of the Joint Chiefs of Staff, Rep. Howard “Buck” McKeon (R.-Calif.) warned that the nation was slipping back into a “September 10th mentality that a solid defense can be dictated by budget choices, not strategic ones.”

“I believe the Department of Defense has already absorbed more than its fair share of cuts,” added McKeon, the panel’s chairman.

Later today, a group of GOP lawmakers, including Sens. Jon Kyl (Ariz.) and Lindsey Graham (S.C.), are addressing defense spending at an event sponsored in part by the conservative American Enterprise Institute and the Heritage Foundation.

Meantime, Gates, who has not addressed the issue of budget cuts since leaving Washington in late July, told an audience in Denton, Tex., on Wednesday night that anything beyond the $400 billion would pose a threat to national security. The slashing of an additional $600 billion from the Pentagon budget – cuts that could theoretically kick in if a bipartisan congressional panel cannot reach an agreement on $1.5 trillion in savings over the next decade – would have a “catastrophic effect,” he said.

Senior Pentagon officials have launched their own offensive to convince lawmakers that further reductions in spending would imperil the country’s security, and Defense Secretary Leon Panetta has said the debt “supercommittee” should focus on tax increases and cuts to nondiscretionary spending, such as Medicare and Social Security, to find needed savings.

With a handful of exceptions, few lawmakers have openly called for the Pentagon budget to be slashed, making the current call to arms among Republicans a bit of staging for what is sure to be a long, arduous political fight.