In their final debate before next week's pivotal primary elections in Florida and Ohio, the Republican presidential candidates on Thursday voiced strong support for a massive increase in the number of American ground troops in the Middle East plus major restructuring at the Department of Veterans Affairs .

The 12th GOP debate marked only the second time that military veterans have taken center stage during the televised events, but it was the latest in the candidates' series of attempts to discredit President Barack Obama's foreign policy — specifically his moves in the Middle East.

Frontrunner Donald Trump, who throughout the campaign has avoided specifics on military manpower and spending, said he'd hear out his generals but believes it could require "20,000 to 30,000" U.S. troops to defeat the Islamic State group in Iraq and Syria, declaring that the small American footprint in the region — currently fewer than 4,000 American ground troops are deployed in support of Operation Inherent Resolve — isn’t enough to defend the nation.

"We don't fight like we used to fight," Trump said. "We used to fight to win. Now we fight for no reason whatsoever. We don't even know what we're doing."

Ohio Gov. John Kasich, who in past debates also has voiced support for increasing ground troops in the region, said the U.S. military needs to "bring all the force you need" to combat the persistent ISIS threat.

"It has got to be 'shock and awe' in the military-speak," he said. "Then once it gets done, and we will wipe them out, once it gets done, it settles down, we come home and let the regional powers redraw the map if that's what it takes."

Texas Sen. Ted Cruz said the next commander-in-chief needs to "do whatever is necessary to utterly defeat ISIS," but he stopped short of specifying how many U.S. ground forces might be needed in the region.

"Right now we're not using a fraction of the tools that we have," he said. "We're not using our overwhelming air power. We're not arming the Kurds. Those need to be the first steps. And then we need to put whatever ground power is needed to carry it out."

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Such plans stand in stark contrast to the Democratic candidates, former Secretary of State Hillary Clinton and Vermont Sen. Bernie Sanders, who have preached limited intervention in the region and careful steps to avoid involving the American military in another open-ended war, a strategy that's close to Obama's .

On VA, the Republican candidates also criticized the president's handling of recent scandals and reforms. Florida Sen. Marco Rubio connected the high rate of suicide among veterans and problems with delivery of department services to a lack of firings in the department.

"The problem is no one's being held accountable," he said. "Even after we passed [reform] laws, no one's been fired for no outreach... No one's been disciplined. No one's been demoted.

"When I'm president of the United States, if you work at the VA and you are not doing a good job, you will be fired from your job."

The issue of accountability has been a recurring theme for Republican critics of the department over the last two years, since revelations of wait time problems and manipulated records forced the resignation of former VA Secretary Eric Shinseki.

Kasich pushed back against a House-backed proposal to trim some GI Bill benefits to pay for other veterans priorities, but he said the department as a whole "needs to be downsized and spread out."

Critics of similar conservative-backed reform consider such changes an effort to privatize the department, a long-held fear for veterans advocates. The Republican candidates have typically portrayed those efforts as expanding choice for veterans frustrated by VA inefficiencies.

The past two Democratic debates have shied away from foreign policy issues, but national security still appears to be a key topic in the general election this fall.

On Thursday, Trump repeated his promises to create "a stronger military, much stronger." Rubio called the armed forces "the best military in the world" but added that it "needs to be rebuilt, because Barack Obama is gutting our military."

Next week features five primary election contests, including Ohio and Florida. Both states are considered must-wins for several of the campaigns, and could force some of the candidates from the race if they fall short.

Leo Shane III covers Congress, Veterans Affairs and the White House for Military Times. He can be reached at lshane@militarytimes.com.