Former President Trump announced his long-awaited selection for vice presidential nominee on Monday during the kickoff of the Republican National Convention, revealing frontrunner Sen. JD Vance, R-Ohio, as his pick. 

"Just overwhelmed with gratitude. What an honor it is to run alongside President Donald J. Trump," Vance wrote on X shortly after midnight. "He delivered peace and prosperity once, and with your help, he'll do it again. Onward to victory!"

Here is what to know about the Republican nominee for vice president.

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J. D. Vance and his wife Usha Vance arrive the first day of the 2024 Republican National Convention at the Fiserv Forum in Milwaukee, Wisconsin

Sen. JD Vance and his wife, Usha Chilukuri Vance, look on as he is nominated for the office of vice president on the first day of the Republican National Convention at the Fiserv Forum on July 15, 2024 in Milwaukee. (Anna Moneymaker/Getty Images)

1. JD Vance once opposed Trump

While Vance is one of Trump's most loyal allies now, he was not always so fond of him. Ahead of the 2016 presidential election, he wrote in a text message to his former roommate, explaining that he goes "back and forth between thinking Trump is a cynical a--hole like Nixon who wouldn’t be that bad (and might even prove useful) or that he’s America’s Hitler."

He once claimed that Trump is "cultural heroin," writing in an essay, "He never offers details for how these plans will work, because he can’t. Trump’s promises are the needle in America’s collective vein."

However, Vance has since had a change of heart. He described his transformation on Fox News, remarking, "I was certainly skeptical of Donald Trump in 2016, but President Trump was a great president, and he changed my mind."

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2. JD Vance had a movie made about his biographical book

In 2016, Vance published his memoir, "Hillbilly Elegy," which quickly became a best-selling book. "Hillbilly Elegy" details his less than glamorous childhood, being raised by his mother and grandmother in Kentucky and Ohio, and the toll addiction takes on families. The story takes readers through the struggles of poverty in rural and Appalachian America. 

A movie was ultimately made about the book, which was distributed by Netflix in 2020. Glenn Close received a nod for Best Performance by an Actress in a Supporting Role at the Academy Awards for her portrayal of Vance's grandmother. 

"I may be White, but I do not identify with the WASPs of the Northeast. Instead, I identify with the millions of working-class White Americans of Scots-Irish descent who have no college degree," Vance said in a 2016 interview about his memoir. 

"To these folks, poverty's the family tradition. Their ancestors were day laborers in the southern slave economy, sharecroppers after that, coal miners after that, and machinists and mill workers during more recent times. Americans call them hillbillies, rednecks or White trash. I call them neighbors, friends and family," he said.

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JD Vance

Former President Trump's pick for vice president, Sen. JD Vance, and his wife Usha Chilukuri Vance arrive at the first day of the Republican National Convention on July 15, 2024, in Milwaukee. (Joe Raedle/Getty Images)

3. JD Vance is a U.S. senator who served in the military

Years before being elected, a young Vance enlisted in the Marines and served in Iraq. In the public affairs section of the 2nd Marine Aircraft Wing, he served as a corporal. 

Vance was elected to the Senate in 2022, defeating his opponent, former Rep. Tim Ryan by more than 200,000 votes. He took office in 2023 and has been serving in the upper chamber since. 

During the campaign, he racked up the endorsement of former President Trump, despite his past remarks about him. He touted Trump's support, which is widely credited with giving Vance an advantage in the Ohio Republican Senate primary. 

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Ukraine President Zelenskyy

Ukraine has been at war with Russia since 2022. (Viktor Kovalchuk/Global Images Ukraine via Getty Images)

4. JD Vance is a strong skeptic of foreign aid to Ukraine

In the Senate, Vance has established a reputation for being particularly skeptical of foreign aid, specifically to Ukraine, which has been embroiled in a war with Russia for over two years. He voted against the $95 billion foreign aid supplemental to Ukraine, Israel and the Indo-Pacific along with several of his Republican colleagues. He has also introduced legislation to provide better oversight of aid to Ukraine. 

Ahead of the vote on additional foreign aid this year, Vance remarked, "I served my country honorably, and I saw when I went to Iraq that I had been lied to — that the promises of the foreign policy establishment were a complete joke."

Peter Thiel

Megadoner Peter Thiel has donated heavily to Republicans. (Michael Cohen/Getty Images for The New York Times)

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5. JD Vance worked in venture capital for megadonor Peter Thiel

After leaving Yale Law School, Vance became a junior investor with Mithril Capital, an investment firm owned by GOP megadonor Peter Thiel, according to Business Insider. He spent two years at the firm before leaving and joining a different firm, Revolution, which was co-founded by Steve Case, who formerly chaired AOL. 

Vance went on to start his own venture capital firm called Narya Capital, which was based out of his home state of Ohio. Thiel was one of the major financial backers who assisted Vance with raising the $93 million he used to start the firm. 

Thiel was a significant supporter of Vance's foray into politics, breaking records when he gave $15 million in total to a PAC supporting the Republican's candidacy for U.S. Senate. 

Get the latest updates from the 2024 campaign trail, exclusive interviews and more at our Fox News Digital election hub.