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President Donald Trump just named a new national security advisor: the same guy he sent to Sweden to deal with rapper A$AP Rocky’s recent assault trial.

“I am pleased to announce that I will name Robert C. O’Brien, currently serving as the very successful Special Presidential Envoy for Hostage Affairs at the State Department, as our new National Security Advisor,” Trump wrote on Twitter Wednesday. “I have worked long & hard with Robert. He will do a great job!”

O’Brien takes over the helm from John Bolton, whom Trump fired last week, although Bolton has repeatedly disputed that he was fired. O’Brien, also a founding partner of a Los Angeles-based law firm, is the fourth national security adviser to serve in Trump’s tumultuous first presidential term. His position does not require Senate confirmation.

A hostage negotiator trained to deal with war-torn countries like Syria and Yemen, O'Brien was dispatched to Stockholm to #FreeRocky at Trump’s request in July. A month earlier, Rocky was arrested and detained for engaging in a street brawl in the nation’s capital, although the U.S. Embassy in Stockholm repeatedly called for his release.

After Trump tweeted advocating for Rocky's freedom, O’Brien threatened “negative consequences” in a diplomatic letter released by the Swedish Prosecution Authority. Rocky was later found guilty of assault but avoided any further jail time and returned to the U.S. Critics saw O’Brien’s arrival as inappropriate, considering he was intervening in an allied country’s affairs, according to the Washington Post.

Apart from getting involved in the Rocky dispute, O’Brien was previously a representative to the United Nations General Assembly after being nominated by George W. Bush in 2005. He joins the Trump administration at a tense time, when Iran is shouldering blame for recent oil rig attacks in Saudi Arabia.