Wisconsin Gov. Scott Walker officially entered the 2016 race Monday, where he confronts the same challenge faced by the governors who’ve run for president before him: convincing voters that running a state qualifies him to be commander in chief.

And after months of foreign policy briefings and trips abroad, taking costly time off from fundraising while wearing the albatross of an early gaffe -- the governor said that he’d fight the Islamic State, or ISIS, the same way he busted Wisconsin’s pro-union protesters -- Walker is still struggling to answer that same question, the biggest of his campaign: How?

“To prosper, however, we need to live in a safe and stable world. That's why I'm for true safety. The commander in chief has a sacred duty to protect the American people,” Walker said. Then he invoked another governor-turned-president: Ronald Reagan. “In my lifetime, the best president when it comes to national security and foreign policy was a governor from California,” he said of his hero.

Reagan created “one of the most peaceful times in modern American history,” he said. “Sadly, today, under the Clinton --,” he stumbled, “or under the Obama/Clinton doctrine, America is leading from behind. And that has us headed toward a disaster.”

As many other candidates have done, he ticked off the list of the “Obama-Clinton” team’s so-called failures, but did not say what he would do about them.

“We've got a president, a president who drew a line in the sand and allowed it to be crossed. A president who called ISIS the J.V. squad, Yemen a success story, and Iran a place we can do business with,” he said.

On a potential deal with Iran over its nuclear program, Walker used the story of Kevin Hermening, an American Marine and hostage in at the U.S. embassy in Tehran, pointing to him in the crowd, to reject the deal. “We need to terminate the bad deal with Iran on the very first day in office,” he said, to cheers. One problem: he’s rejecting a deal he’s never seen because it doesn’t yet exist. As of this writing, negotiations continue.

For all of Walker’s rhetoric as a “fighter,” he has largely avoided confronting foreign policy since the ISIS gaffe and another poor showing while on a trip abroad to England in February. He dodged foreign policy related questions and showed discomfort with the subject matter -- and simply puzzled audiences -- with misplaced references, such as to his state’s dairy products. In a later sojourn to Israel in May, Walker kept away from the press, but that didn’t keep him from touting the visit in his speech Monday.

In Waukesha, Walker gave a typically tough-talking stump speech short on specifics on national security issues.

“The greatest threat to future generations is radical Islamic terrorism and we need to do something about it,” Walker said, without offering what he would do.

Last week, Defense Secretary Ash Carter said there are roughly 3,550 American personnel at six locations in Iraq, and the U.S. has conducted more than 5,000 airstrikes against ISIS. He outlined nine areas of effort.

Walker’s national security credibility faces stronger scrutiny as the Republican field has ballooned and the party tries to ensure 2016 is a national security election. The GOP is seeking to capitalize on public anxiety about ISIS and the Obama administration’s strategy to defeat it, in part to preempt the likely Democratic nomination of former Secretary of State Hillary Clinton.

The GOP’s strategy becomes a disadvantage for candidates like Walker, particularly in contrast to his closest rivals in the top-tier of polling, such as Sen. Marco Rubio of Florida, who sits on key committees, or former Florida Gov. Jeb Bush, who at least through his family name can also claim a front-row seat to the toughest foreign policy decisions.

“In the Republican field, there are some that are good fighters, but they haven’t won those battles,” Walker said. “There are others that have won elections, but haven’t consistently taken on the big fights. You’ve shown you can do both.”

Walker is a hero among a certain sect of the GOP for union-busting and an aggressively conservative legislative agenda. But his approval ratings are around 41 percent, which puts him only above Louisiana Gov. Bobby Jindal and New Jersey Gov. Chris Christie in a popularity contest -- not company he wants to be in, considering these candidates’ low polling in the presidential race.

And for all his Midwestern charm and the well-documented innate political instinct that has won him three elections in four years, and enabled his survival in an attempted recall, Walker’s lack of experience can also communicate to voters insufficient ingenuity and intelligence to handle the complex global security landscape. He consistently uses “safety” instead of national security, a term he views as elitist and too inside-the-Beltway.

Walker used familiar national security rhetoric to fill out his speech, however. On Russia, he said, “We need to stop the aggression of Russia into sovereign nations.” On China, “We need to stop China's cyber attacks, slow their advances into international waters.”

“And we need to have the capacity to protect our national security interests here and abroad, and those of our allies,” he continued. “That begins by rebuilding the defense budget.”

“Our goal should be peace,” Walker said, to chants of “USA!” “But there will be times when America must fight. And if we must, Americans fight to win.”

What he didn’t say, was: How?