President Trump on Thursday took aim at one of his favorite political targets – fellow Republican, Sen. John McCain – after McCain questioned the success of a military raid in Yemen that resulted in the death of a Navy SEAL.

McCain had said in a Wednesday statement that he “would not describe any operation that results in the loss of American life as a success.” White House Press Secretary Sean Spicer later fired back, saying “anyone who undermines the success of that raid owes an apology and [does] a disservice,” but didn’t mention McCain by name. Trump, however, held nothing back.

“Sen. McCain should not be talking about the success or failure of a mission to the media. Only emboldens the enemy! He’s been losing so long he doesn’t know how to win anymore, just look at the mess our country is in – bogged down in conflict all over the place,” Trump wrote in a series of morning tweets. “Our hero Ryan died on a winning mission (according to [Secretary of Defense] General Mattis), not a ‘failure.’ Time for the U.S. to get smart and start winning again!”

While the military reported taking a trove of information following the Jan. 29 nighttime raid on an Al Qaeda compound, Navy SEAL William “Ryan” Owens was killed and three other troops were wounded. U.S. forces also were forced to destroy an MV-22 Osprey aircraft after a “hard landing.”

"Several of [the Trump tweets] cracked me up," McCain said later Thursday. "I can't comment on what the president does and I won't, but one of the things I've learned over the years here -- frankly, one of the guys I learned this from was Ted Kennedy -- he said you can ferociously defend your position or take the offense, but not get personal and you can move onto another issue or move on.

"I've tried to move on in the senate. I haven't always succeeded because of my temper, but generally speaking...I love to argue this...people I disagree with, I just don't get personal with it."

But while McCain didn't take on the president directly, several Democratic senators jumped to the Arizona Republican's defense on Thursday.

"When President Trump assaults Senator McCain, he better watch out," said Sen. Bill Nelson, D-Fla. "Because this is a guy who knows what he's talking about and not only has he walked his talk, he's been there. And that's a dangerous area for president trump to continue to trash John McCain."

Trump has frequently attacked McCain, a moderate GOP legislator who often has been critical of the president.

The war of words began when Trump said in July 2015 that McCain, who was a prisoner during the Vietnam war, was “not a war hero.”

“He was a war hero because he was captured,” Trump said. “I like people who weren’t captured.”

Trump quickly followed that controversy by lambasting McCain for problems at the VA. In October 2016, as Trump was being pilloried after a decade-old audio surfaced that featured Trump making crude remarks, Trump hit McCain for not supporting him.

“The very foul mouthed Sen. John McCain begged for my support during his primary (I gave, he won), then dropped me over locker room remarks!” Trump tweeted Oct. 11.

When Trump’s executive order temporarily restricting immigration from seven mostly Muslim countries drew a rebuke from McCain and Sen. Lindsey Graham, Trump again took to Twitter.

“The joint statement of former presidential candidates John McCain & Lindsey Graham is wrong – they are sadly weak on immigration,” he wrote. “The two Senators should focus their energies on ISIS, illegal immigration and border security instead of always looking to start World War III.”

Fox News' Peter Doocy and Jason Donner contributed to this report.