President Donald Trump revived his attacks against Sen. Richard Blumenthal over the Connecticut Democrat’s misleading claims about having fought in the Vietnam War.

While on vacation Monday, Trump fired off several tweets about Blumenthal, calling him a “phony Vietnam con artist” for claiming he “served in Vietnam” when he did not.

Interesting to watch Senator Richard Blumenthal of Connecticut talking about hoax Russian collusion when he was a phony Vietnam con artist! — Donald J. Trump (@realDonaldTrump) August 7, 2017

Never in U.S.history has anyone lied or defrauded voters like Senator Richard Blumenthal. He told stories about his Vietnam battles and.... — Donald J. Trump (@realDonaldTrump) August 7, 2017

...conquests, how brave he was, and it was all a lie. He cried like a baby and begged for forgiveness like a child. Now he judges collusion? — Donald J. Trump (@realDonaldTrump) August 7, 2017

Trump’s history with Vietnam is similar to Blumenthal’s. The senator obtained at least five deferments from military service between 1965 and 1970, according to The New York Times. Trump also deferred the draft five times ― four times for education and once after he was diagnosed as having bone spurs in his heels.

Blumenthal was eventually placed in the Marine Corps Reserve, where he served for six years in the U.S. Despite never going overseas, he made claims to the contrary, talking on multiple occasions about serving during Vietnam and making references to the time “when we returned” from the war.

“We have learned something important since the days that I served in Vietnam,” Blumenthal said to a group in 2008, according to The New York Times.

Trump’s latest attack on Blumenthal came after the senator appeared on CNN Monday morning, arguing that the investigation into Russian efforts to influence the 2016 presidential election “must be pursued” and that special counsel Robert Mueller must be protected throughout the process.

Blumenthal responded to Trump’s “bullying” with tweets of his own, telling the president that “this issue isn’t about me.”

Mr. President: Your bullying hasn't worked before and it won't work now. No one is above the law. — Richard Blumenthal (@SenBlumenthal) August 7, 2017

This issue isn't about me - it's about the Special Counsel's independence and integrity. — Richard Blumenthal (@SenBlumenthal) August 7, 2017

Trump has attacked Blumenthal several times in the past. He tweeted against the senator in February after Blumenthal said then-Supreme Court nominee Neil Gorsuch found Trump’s attacks on judges “disheartening” and “demoralizing.”

In May, Blumenthal argued a special prosecutor was needed to investigate the Trump campaign’s ties to Russia after the president fired FBI Director James Comey. Trump, tweeting again, called Blumenthal “one of the greatest military frauds in U.S. history.”

The Monday morning posts were part of a larger tweetstorm that also included a rant against “fake news.”

Trump tweeted about Blumenthal again Monday afternoon.

I think Senator Blumenthal should take a nice long vacation in Vietnam, where he lied about his service, so he can at least say he was there — Donald J. Trump (@realDonaldTrump) August 7, 2017

Blumenthal, in another CNN appearance after the latest Trump tweet, declined to directly respond to the president’s comments. He repeatedly told CNN anchor Wolf Blitzer that he would rather focus on protecting “the independence and integrity” of Mueller’s investigation.

“It is not about me,” Blumenthal said. “I have no idea what is in [Trump’s] mind. What I do know is I will not be distracted by this bullying. These bullying tweets reinforce for me the need for a piece of legislation ... to prevent the firing of the special counsel, Robert Mueller, whom he has also sought to intimidate.”

This article has been updated with Blumenthal’s response to the latest Trump tweet attacking him.