Former President Donald J. Trump wrapped himself in military imagery on Monday, attacking the Biden administration over its withdrawal from Afghanistan. Observing the third anniversary of a deadly suicide bombing in Kabul, the Afghan capital, he visited Arlington National Cemetery, then later spoke in Detroit to a gathering of National Guard members.

During his remarks in Detroit, at a conference for the National Guard Association of the United States, Mr. Trump blamed President Biden and Vice President Kamala Harris for the bombing and America’s chaotic withdrawal from Afghanistan, which he argued led to the conflicts in Gaza and Ukraine.

“Caused by Kamala Harris, Joe Biden, the humiliation in Afghanistan set off the collapse of American credibility and respect all around the world,” Mr. Trump said. He added, “It gave us Russia going into Ukraine. It gave us the Oct. 7 attack on Israel, because it gave us lack of respect.”

As he has attacked Democrats over foreign policy and national security issues this year, Mr. Trump, who often highlights his allegiance to the troops, has made the withdrawal from Afghanistan in 2021 a central focus. He and his allies have pointed frequently to the suicide bombing at Abbey Gate at the Kabul airport on Aug. 26, 2021, which killed 13 American service members and as many as 170 civilians, arguing that the Biden administration’s handling of the event showed a disregard for American service members.

Still, Mr. Trump has been fending off criticism from Democrats and some veterans groups that he has been insufficiently respectful of the military and has made comments in which he has appeared to mock, attack or express disdain for service members who are wounded, captured or killed.

During their national convention, Democrats repeatedly brought up the claim that Mr. Trump, while president, called veterans “suckers” and “losers.” And this month Mr. Trump drew the ire of veterans groups after he described the Presidential Medal of Freedom, which honors civilians, as being “much better” than the Medal of Honor, the nation’s highest military honor, because service members who receive it are often severely wounded or dead.

Mr. Trump and his campaign drew a contrast on Monday between his decision to visit Arlington National Cemetery in Virginia, where he laid three wreaths at the Tomb of the Unknowns to honor the troops killed at the airport attack, and Ms. Harris’s role in the withdrawal.

In an interview with CNN in 2021, Ms. Harris said she was the last person in the room when Mr. Biden decided to pull out from Afghanistan. Mr. Trump has pointed to that remark as proof that she was directly involved with and bore some responsibility for the chaotic withdrawal.

The Biden administration has noted that Mr. Trump made a deal with the Taliban in 2020 that set a timeline for America’s exit, and Democrats have argued that Mr. Trump flip-flopped on the withdrawal after Mr. Biden saw it through.

In a statement on Monday, Ms. Harris mourned the loss of the 13 American soldiers killed in the airport attack and said she honored those who served in the 20-year war in Afghanistan. She also reiterated her support for Mr. Biden’s “courageous and right decision” to withdraw troops from Afghanistan.

Ammar Moussa, a spokesman for the Harris campaign, attacked Mr. Trump’s leadership. “The Biden-Harris administration inherited a mess from Donald Trump,” he said in a statement. “Trump wants America to forget that he had four years to get out of Afghanistan, but failed to do it. ”

During his speech in Detroit, Mr. Trump noted that he was criticizing “not that we withdrew, but the way we did it.” He repeated his promise to demand the resignations of senior miliary officials involved in the withdrawal. He also repeated his insistence that he could bring the wars in Ukraine and Gaza to an end immediately after being elected, though he has yet to offer specific plans for doing so.

As he spoke to Air and Army National Guard officers and service members and their families, Mr. Trump insisted that Democrats were “waging war” on the “rights and liberties” that the military was deployed to defend.

And Mr. Trump, whose false claims of widespread fraud in the 2020 election led some of his supporters to attack the Capitol and prevent the peaceful transfer of power, insisted he would “make American democracy great again.”

Mr. Trump covered a range of topics in his Detroit speech, though he largely stayed focused on issues he could tie to the National Guard, like military concerns and foreign policy. He used the deployment of the Texas National Guard to the border as a peg for extensive remarks on immigration. And as he attacked Ms. Harris and her running mate, Gov. Tim Walz of Minnesota, for voicing support for protesters after the police killing of George Floyd in 2020, Mr. Trump bragged about supporting the deployment of the National Guard to stop looting or violence.

Still, Mr. Trump’s remarks veered occasionally into asides, including questioning Harris’s becoming the Democratic nominee without winning a vote in a primary race, accusing Democrats of weaponizing the Justice Department against him and attacking Europeans for taking advantage of America on trade.

Mr. Trump also promised to create a separate Space National Guard to work with Space Force, the military branch whose creation he oversaw. He again bragged about telling NATO members that he would not defend them from Russian aggression unless they raised their military spending. NATO members have made informal commitments to spend 2 percent of their gross domestic product on their militaries, and more than 20 of the alliance’s 32 members were on track to hit that target as of July.

But in his speech, Mr. Trump said that he would insist NATO members “spend at least 3 percent,” a target that he could not set unilaterally but that raises questions about his continued commitment to the alliance.

Mr. Trump at one point invited Tulsi Gabbard, a former congresswoman, who has since left the Democratic Party, to the stage to formally endorse him. She served two combat tours in the Middle East and is helping him with debate preparations.

After his cemetery visit earlier on Monday, he stopped at a Vietnamese restaurant in Falls Church, Va., where he appeared with Hung Cao, who is the Republican Senate candidate in the state and a retired Navy captain. Standing next to Mr. Cao, he lamented the deaths at the Abbey Gate bombing, saying “these are people that should have never been killed.”

Mr. Trump and his campaign are hoping to flip Virginia, which has not been won by a Republican in a presidential race since 2004. At the restaurant, he said he thought Mr. Cao had strong chances of winning, even though Virginia was “traditionally not necessarily for Republicans, but I’m not the average Republican and neither are you.” In front of a crowd of Asian Americans, Mr. Trump also said he believed Mr. Cao’s “name alone should get you elected, right?”

Chris Cameron contributed reporting from Falls Church, Va.