Reprising a familiar battle between the two Republican presidential candidates, Donald Trump and Jeb Bush butted heads Saturday night over former president George W. Bush and U.S. involvement in the Iraq war.

"Obviously the war in Iraq was a big fat mistake, alright?" Trump said at CBS News' GOP debate in Greenville, South Carolina. "George Bush made a mistake, we can make mistakes. But that one was a beauty."

Trump went on to tie the war to his current White House rival, Jeb Bush.

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"It took Jeb Bush -- if you remember at the beginning of his announcement when he announced for president, it took him five days -- 'It was a mistake, it wasn't a mistake,' -- it took him five days before his people told him what to say," Trump said. "[W]e should have never been in Iraq, we have destabilized the Middle East."

"They lied. They said there were weapons of mass destruction -- there were none. And they knew there were none," he added.

Bush snapped back: "I'm sick and tired of Barack Obama blaming my brother for all of the problems that he's had," he said. "I could care less about the insults that Donald Trump gives to me. It's blood sport for him...but I am sick and tired of him going after my family. My dad is the greatest man alive in my mind. While Donald Trump was building a reality TV show my brother was building a security apparatus to keep us safe and I'm proud of what he did."

Interrupting Bush, Trump reminded the audience that "the World Trade Center came down during your brother's reign.

Bush attempted to defend the rest of his family -- particularly his mother, Barbara Bush, who has recently hit the campaign trail to support her son's presidential run -- from Trump's attacks.

"He's had the gall to go after my mother," Bush said. "My mom is the strongest woman I know."

Trump interjected, "She should be running."

To that, Bush responded: "This isn't about my family or his family -- this is about the South Carolina families who need someone to be a commander-in-chief."