Sparks could fly in 'historic' Hagel confirmation hearings NEW: Hagel vows to work to advance "freedom, decency, and humanity" Obama says Hagel is "the leader that our troops deserve" (CNN) -- He forged his views of war and the military as a young man in mine-plagued fields of Vietnam. Now Chuck Hagel may become the first Vietnam veteran and first enlisted soldier to serve as U.S. defense secretary. He would also be one of the few Pentagon chiefs ever to have been wounded in war, President Barack Obama said in announcing his selection on Monday to take over for outgoing Defense Secretary Leon Panetta. Obama said Senate confirmation of Hagel would be "historic." But for Hagel, the road from nomination to confirmation is packed with obstacles -- political landmines that could derail the effort. "Chuck Hagel is the leader that our troops deserve," the president said, calling him a "patriot" who fought alongside his brother in Vietnam -- and each saved the other. Hagel still "bears the scars" from the battles "he fought in our name," Obama said. He understands that sending young Americans to fight and bleed in the dirt and mud is something that we only do when it's absolutely necessary. Hagel said in return that he was "honored by your trust and confidence in me and not unmindful of the immense responsibilities that go with it." Praising troops who serve with "such dignity and selflessness," Hagel expressed support for military families as well, specifically "who have sacrificed so much over more than a decade of war" in Afghanistan. He vowed to work to "strengthen our country's alliances and advance global freedom, decency and humanity" in the effort to "build a better world for all mankind." Obama also announced his selection of counterterrorism adviser John Brennan to lead the CIA. Noting that Hagel is a Republican, Obama said the selection "represents the bipartisan tradition that we need more of in Washington." But much of the Republican establishment begs to differ. "He has long severed his ties with the Republican Party," Sen. Lindsey Graham, R-South Carolina, said Sunday. Graham called the selection "an in-your-face nomination by the president to all of us who are supportive of Israel." Questions over Hagel's support of Israel are just one of the controversies swirling around him. Numerous concerns could lay the groundwork for sparks at Senate confirmation hearings. Read more: Choice in Hagel sparks mixed reactions "Let's just say if Chuck Hagel is nominated," CNN Chief Political Correspondent Candy Crowley said Sunday, "set your TiVo for the hearings." Some of flashpoints that his critics point to are the same ones that his vocal supporters like. Hagel has said he favored U.S. negotiations with Iran and opposed increased sanctions. He has supported Israel entering negotiations with Hamas, though also insisted Hamas end terrorism and accept Israel's right to exist. And the former U.S. senator from Nebraska has criticized U.S. policy on Afghanistan, including a 2009 "surge" that sent in 30,000 additional troops. If he becomes defense secretary, Hagel will face the challenge of ending that U.S.-led war and overseeing a smaller training force in the country. But the controversies surrounding Hagel aren't just about his policy positions. They're also about his views. Some are bothered by a comment he made in 1998 about an ambassadorial candidate being "aggressively gay" -- which he recently apologized for. And in a 2007 interview, he said a "Jewish lobby intimidated lawmakers" -- sparking heated criticism. A rabbi in Hagel's home state insists he is "a friend of Israel." Read more: White House officials reach out to Jewish community to answer Hagel concerns Graham told CNN he believes that if confirmed, Hagel "would be the most antagonistic secretary of defense towards the state of Israel in our nation's history." Sen. Chris Murphy, a freshman Democrat from Connecticut, said that he believes "Republicans are spoiling for a fight." The rhetoric over Hagel on both sides is ratcheting up. Past controversies have led presidents to pull some nominations. But the bumpy road ahead is unlikely to faze the 66-year-old at the center of it all. "Chuck Hagel is not afraid of challenge -- or risk," his biographer, Charlyne Berens, wrote in 2006. All I can to prevent war If he becomes defense secretary, Hagel will be tasked with carrying out the orders of a president who vowed to end two wars -- Iraq and Afghanistan. Ending and avoiding war are part of what he committed his life to while in his 20s in Vietnam, Berens writes. After a year of Vietnam's miserable heat, nearly constant danger, and violent campaigns like the Tet Offensive, Chuck Hagel came back to the United States ready to get on with things -- and with both a loyalty to the U.S. military and a belief he should do all he could to prevent his nation's being involved in another war. Read more: Chuck Hagel's views on war forged by Vietnam experience His fierce opposition to the Iraq War, launched by President George W. Bush, went far toward creating the schism that now exists between him and the Republican establishment. "The damage this war has done to our country will play out for years to come," he wrote in his 2008 book, "America: Our Next Chapter." "While it is easy for nations to blunder into war, they never blunder into peace," he added. "If I ever get out, if I ever can influence anything, I will do all I can to prevent war," he told Berens. His opposition to the 2009 surge in Afghanistan put him at odds with the president who is now nominating him. The surge showed a rare moment of support for Obama among many Republicans, with Hagel as a standout exception. But his willingness to be an independent voice has won him cheers as well. "He's a guy with really serious foreign policy chops and someone, frankly, who hasn't been afraid to depart from his party when he thought they were wrong," Murphy said in an interview with CNN. Apology for 'insensitive' remark As defense secretary, Hagel would oversee a military that recently dropped its "Don't Ask, Don't Tell" policy for gay and lesbian personnel -- a policy he supported. Battles continue over whether same-sex marriages can take place at some U.S. bases. So his perspective on gays and lesbians carries particular weight. In 1998, he opposed James Hormel, an openly gay man, for an ambassadorship. Hagel questioned whether Hormel was suitable, describing him as "openly, aggressively gay." In December, 14 years later, he apologized, calling those comments "insensitive." They do not reflect my views. I apologize to Ambassador Hormel and any LGBT (Lesbian, Gay, Bisexual, and Transgender) Americans who may question my commitment to their civil rights. The Log Cabin Republicans, a group that supports gay rights, argues the apology was "too little, too late." But gay rights activist Rick Jacob, head of the Courage Campaign, said he supports the president making his choice for defense chief, and noted that "no one trying to derail (Hagel's) nomination attacks his qualifications." Hagel's support for Israel questioned Concerns about Hagel's support for Israel could prove to play a big role in confirmation hearings. In addition to calling for talks with Iran, which openly antagonizes Israel, Hagel has spoken out against some additional sanctions -- a cornerstone of Obama's foreign policy aimed at pressuring Tehran amid questions about the country's nuclear program. Graham noted that Hagel has wanted Israel to talk with Hamas, a "terrorist group that lobs thousands of rockets into Israel. He also was one of 12 senators who refused to sign a letter to the European Union trying to designate Hezbollah as a terrorist organization. That and questions about his remark on a "Jewish lobby" have drawn criticism from across the political spectrum and from some Jewish organizations. "Senator Hagel would not have been my first choice, but I respect the president's prerogative," Abraham Foxman, head of the Anti-Defamation League, said in a statement. I trust that the confirmation process will provide an opportunity for Sen. Hagel to address concerns about his positions. ... I particularly hope Senator Hagel will clarify and explain his comments about the "Jewish Lobby" that were hurtful to many in the Jewish community." Hagel joined two other senators in introducing a resolution in June, 2007, pushing for a two-state solution to the Israeli-Palestinian conflict. The resolution called on Hamas "to recognize the State of Israel's right to exist, to renounce and end all terror and incitement, and to accept past agreements and obligations with the State of Israel." Rabbi Aryeh Azriel of Temple Israel in Omaha, Nebraska, a longtime friend of Hagel's, told CNN that Hagel is "definitely a friend of Israel. He is independent, has wonderful, fresh ideas to try to reengage the discussion about the Middle East. Azriel grew up in Israel, and said he personally supports the idea of doors being "opened for negotiation even with Hamas and Hezbollah." 'Thorough vetting' ahead Sen. Mitch McConnell, the Republican leader in the Democratic-controlled Senate, vowed Hagel would receive a "thorough vetting" just like any other presidential nominee. Hagel, in his remarks Monday, emphasized his willingness to speak his mind. "Mr. president, I will always give you my honest and most informed council," he vowed. While he did not discuss his views on any of the flashpoint issues during his brief comments, a line from Hagel's 2006 biography offers insight into how he would lead at the Pentagon. CNN's Mike Mount, Kevin Liptak, Jill Dougherty, and Catherine Shoichet contributed to this report.