Hanoi, Vietnam (CNN) It can be hard in this communist capital to avoid vestiges of the conflict known here as the American War. The Hanoi Hilton, a ruefully nicknamed prison, is the city's main tourist site. The Metropole Hotel, Hanoi's finest, has an underground bomb shelter that's been restored for tours.

Yet President Donald Trump, who is of the age to have served in the war but did not, seemed less taken with the historic symbols Wednesday than with his long-simmering dispute with a Democratic senator, who he has accused of manufacturing his wartime credentials.

At the same moment, Trump himself was being freshly accused of manufacturing a medical reason to avoid compulsory military service during the Vietnam era. This time the claim came from his former fixer Michael Cohen, who is also preparing to accuse the President of being a racist conman during congressional testimony on Wednesday.

It all added up to renewed questions over the President's views of wartime service as he pays his second visit to Vietnam, this time to try and extract a nuclear deal from North Korean leader Kim Jong Un. Unlike his past three predecessors, Trump has not weighed in at length about the US legacy here -- of agent orange, unexploded ordnance and millions dead.

In a city that still displays the flight suit and parachute belonging to the late Sen. John McCain -- once besmirched by Trump as "not a war hero" -- Trump's own relationship to the war is again being scrutinized.

"I have now spent more time in Vietnam than Da Nang Dick Blumenthal, the third rate Senator from Connecticut (how is Connecticut doing?)," Trump boasted on Twitter after spending the morning in meetings with officials from the Vietnamese government.

"His war stories of his heroism in Vietnam were a total fraud - he was never even there," Trump continued. "We talked about it today with Vietnamese leaders!"

That conversation wasn't described in the White House's official readout of the session, which transpired in the mustard-hued presidential palace adorned with flowers and plenty of Ho Chi Minh busts. Instead, White House press secretary Sarah Sanders said the men discussed "deepening political, security, economic, and people-to-people ties, and through cooperation on humanitarian and legacy of war issues."

But if Trump raised Blumenthal's war history with his foreign hosts, it would perhaps not be a surprise for a President who is known to carry a grudge and use whichever venue -- however inappropriate -- to litigate it.

That was how he approached his relationship with McCain, even as the Republican senator was nearing the end of his life. Shortly after announcing his run for president in 2015, Trump deemed the Republican -- who was imprisoned and tortured in Hanoi after his plane crashed into a lake -- as wrongly cast as a war hero.

"I like people that weren't captured," Trump said, a remark that was instantly condemned by members of both parties, but Trump later told people he didn't regret it.

That launched a famously bitter relationship between the two men, which spiraled after McCain voted "no" on a piece of health care legislation that Trump was advocating. Even as the senator was in the final stages of brain cancer, Trump did not cease in his criticisms. And he hasn't mentioned him on either of his two visits to Hanoi, unlike his predecessor Barack Obama, who defeated McCain in the 2008 presidential contest and hailed McCain's service during a speech here in 2016.

Instead, Trump has seemed more intent on lobbing accusations at another senator, Blumenthal, who admitted in 2010 to misrepresenting his military service after saying he had been "in" Vietnam. Blumenthal served in the Marine reserves in Washington, not Vietnam, during the war.

Even as US officials were negotiating the summit's location with their North Korean counterparts, Trump had Blumenthal on his mind. Asked in the Cabinet Room earlier this month whether the talks would be held in Da Nang, the seaside resort where the first conventional US combat unit landed in 1965, Trump's mind went immediately to his festering grudge.

"Gee, Da Nang. Who does Da Nang remind me of, huh?" he said. "A certain senator. It's a certain senator that said he was a war hero when he wasn't. He never saw Da Nang."

Neither did Trump, it turns out, until he traveled there in 2017 for a summit of Asian leaders. While he was the right age to be conscripted into service by the draft, he received a medical deferment for bone spurs on his feet.

Decades later, he would make light of his situation in interviews, telling Howard Stern -- reported by CNN's KFile -- that navigating an active sex life was his "own Vietnam."

"Dating is like being in Vietnam. Dating is like being in Vietnam. It's the equivalent of a soldier going over to Vietnam. It's like war out there," Trump said.

The bone spurs deferment has received scrutiny in the past, including when the daughters of the podiatrist who issued the diagnosis told The New York Times their father did so as a "favor" to Trump's father Fred. Cohen will claim in his testimony on Wednesday, it was a convenient way for a child of wealth to avoid military service.

For his part, Trump has stuck to his story about the bone spurs, but never explained how he went from an athletic young man in college to someone who was medically ineligible for combat.

Questioned early in the campaign about the topic, Trump couldn't remember which foot suffered from the condition , telling reporters, "you'll have to look it up." The campaign soon said that Trump "received a minor medical deferment for bone spurs on both heels of his feet."

The campaign also said, "the medical deferment was expected to be short-term" and that Trump entered into the draft lottery but was lucky to receive a high number, thus avoiding the draft.

"Although he was not a fan of the Vietnam War, yet another disaster for our country, had his draft number been selected he would have proudly served, and he is tremendously grateful to all those who did," the Trump campaign said in its statement, which was issued in July 2015.

Trump has repeated that explanation about the lottery number many times over the years.

While mulling his first presidential bid for the 2000 election, Trump told NBC News , "my date, which was June 14, was a very high date in the lottery, so I never got drafted, so I was very lucky." In 2011, when he considered challenging President Barack Obama, Trump told a local Fox affiliate in New York , "I was watching as they did the draft numbers and I got a very, very high number."

Regarding the bone spurs, Trump told The New York Times in 2016 that, "I had a doctor that gave me a letter -- a very strong letter on the heels ... it was difficult from the long-term walking standpoint." He also claimed that the condition "healed up" after a certain period of time.

But, according to prepared testimony from Cohen, Trump told his lawyer: "You think I'm stupid, I wasn't going to Vietnam."

"Mr. Trump tasked me to handle the negative press surrounding his medical deferment from the Vietnam draft," Cohen will say. "Mr. Trump claimed it was because of a bone spur, but when I asked for medical records, he gave me none and said there was no surgery. He told me not to answer the specific questions by reporters but rather offer simply the fact that he received a medical deferment."

Trump will be ensconced in his hotel during Cohen's televised testimony, fresh from a social dinner with Kim at the Metropole Hotel. White House officials have suggested there is little they can do to prevent Trump from staying awake into the night to watch.

Cohen, whose dramatic break with Trump has provided one of the ongoing subplots of the larger Russia investigation, plans to make reference to Trump's location in his opening statement.

"I find it ironic, President Trump, that you are in Vietnam right now," he'll say.