What do we mean when we say anti-war Republicans? Is the Republican party becoming more anti-war? If we look at history we will see that historically the Republican Party has been much less hawkish than it is now. Republicans in the early part of the 20th century were by and large non-interventionist. They opposed Woodrow Wilson’s efforts to get the United States involved in World War I. Robert Taft, son of former president and chief justice William Howard Taft, was a leading conservative Republican in the 1940s and ‘50s. He opposed wars of aggression. Even Dwight D. Eisenhower could been seen as being less of a war hawk than many modern Republicans, even though he was the top general of World War II. He exposed what he called the “military industrial complex” in his farewell address. This all started to change after World War II and with the onset of the Cold war. The “old right” that had supported a less intrusive foreign policy began to give way to a more interventionist philosophy in about the 1960s.
Part of the cause of the shift toward a more aggressive foreign policy in the Republican Party was the rise of neoconservatism. What neoconservatism (it’s adherents sometimes referred to by the shortened neocon) is exactly is not always well-defined but it is essentially a redefining of what it means to be conserve. The idea behind neoconservatism is that it’s supportive of American imperialism and exceptionalism, and pushes the idea that we should spread democracy to the rest of the world, never mind that the other country may not even want our help. They believe that the U.S. is in some way morally superior and therefore has a duty to be the world’s policeman or the watchtower of the world. It was championed by Irving Krystol and the magazine Commentary, and it’s leading advocate today could be seen to be William Krystol, Irving’s son. The movement eventually took over the leadership of the Republican Party, but there seems to be a current trend of an increased number of Republicans going away from it now. Neoconservatism has become associated with George W. Bush’s administration although interestingly, when he first ran, Bush denounced the idea of nation-building. When in office however, he was influenced by such neoconservative figures as Paul Wolfowitz and Karl Rove.  Similar to Bush, when campaigning, Barack Obama criticized Bush’s foreign policy, but since he was elected, has embraced much of it. The aforementioned Bill Krystal even called Obama a “born again neo-con”. 
There have been a number of anti-war conservatives who have felt disenfranchised by Republican Party due to the hostility they received, people such as Pat Buchanan, a leader of what is called paleoconservatism, a non-interventionist rival to the neocons. However on the other hand there seems to be a shift in the Republican Party in some respects toward a less aggressive foreign policy. Ron Paul initially lead the way and even criticized Bush and now his son, Rand Paul, who is in the Senate, but others have joined it now including Congressmen Walter Jones and Justin Amash. John McCain, one of the leading neoconservatives and the Republican presidential nominee in 2008, has been criticized by many Republican figures for criticizing Rand Paul’s filibuster which mostly focused on the use of drones. Even the rhetoric is changing. Many republicans were for troop withdrawals, something they wouldn’t have supported years ago. Public opinion among conservatives seems to have been shifting that way and thus grassroots candidates tend to do better in this regard while many in the Republican leadership would like to hold onto a more neoconservative bent.
The fate of anti-war Republicans can also be seen in the recent hearings to confirm Chuck Hagel as Secretary of Defense. Hagel a Republican, was criticized by his fellow Republicans largely due to his opposition to the Iraq war. Many of these same Republicans had no problem voting to approve John Kerry, a Democrat, as Secretary of State by a large margin only weeks earlier. While this may show that there is still a strong neoconservative element, we can hold out that the landscape will continue to shift for the better.
It often seems that the party not in power will oppose wars started by the other party but not their own, usually coming up with an excuse for the reason it’s OK when their guy does it. Many Republicans opposed Obama’s intervention in Libya. So is this shift genuine or just a response to abuses from the Obama administration? I think it is too soon to say for sure, but the fact that so many Republicans have spoken out against fellow Republicans such as John McCain is a good sign.