Palm Beach, Florida - Donald Trump and his campaign are already on the against Tim Walz, Kamala Harris' new running mate, and they're reviving a strategy he has become infamous for: targetting his service record.

The New York Post recently published an interview with Thomas Behrends, a former National Guardsman who claimed he was the soldier who replaced Walz after he retired two months before their unit was deployed to Iraq.

Behrends, who made the same allegations in 2018 when Walz ran for Governor of Minnesota, called the Democrat "a traitor," and described his actions as saying "screw you" to the US.

His story has caught the attention of Trump and his allies, who have begun sowing doubt about Walz's record.

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On Wednesday, during a press conference in Michigan, Trump's running mate JD Vance tried out the new attack for the first time, using his own military career to bolster his argument.

"When the United States of America asked me to go to Iraq to serve my country, I did it," Vance, who spent six months deployed in Iraq during his four years as a combat correspondent in the Marine Corps, argued.

Vance went on to state that Walz "dropped out... a fact that he's been criticized for aggressively by a lot of the people that he served with," and accused him of "stolen valor."

"I think it's shameful," he added.

According to The Independent, military records show that Walz joined the National Guard at 17 years old, and retired two months before his unit was notified of their deployment.

The Trump campaign's latest attempt at attacking their opposition comes as they struggle to find an effective strategy to take on Harris and Walz.

Critics have pointed out that Trump has used the tactic of sowing doubt about the service records of his political rivals in the past.

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Back in 2004, the Trump campaign pushed their "Swift Boat" campaign against Democratic presidential nominee John Kerry, which aimed to discredit his service record. The term refers to a type of Navy vessel that Kerry commanded during the Vietnam War.

During his 2016 presidential campaign, Trump infamously insulted the late former Republican Senator John McCain, who had spent five years as a prisoner of war during Vietnam.

Trump argued that McCain wasn't a "war hero" because "I like people who weren't captured."

Other critics have also been quick to point out that Trump dodged the Vietnam War draft five times, once arguing he had bone spurs.

In a response to Vance's remarks, The Harris Walz campaign said in a statement, "Governor Walz would never insult or undermine any American's service to this country – in fact, he thanks Senator Vance for putting his life on the line for our country."