WASHINGTON – By choosing former ambassador John Bolton to replace H.R. McMaster as his third national security adviser, President Donald Trump has turned to a conservative hard-liner who favors military action in many cases.

Trump announced late Thursday evening on Twitter his choice, which will take effect April 9th. While the president thanked McMaster for an “outstanding job,” it was widely known that the two men did not get along and that Trump often bridled at McMaster’s domineering style.

Bolton is an ardent and outspoken hawk who served in the administration of Republican President George W. Bush and recently has been a frequent commentator on Fox News.

Here are five things to know about the new national security advisor:

  • He supports preemptive strike against North Korea.

“It is perfectly legitimate for the United States to respond to the current ‘necessity’ posed by North Korea’s nuclear weapons by striking first,” he wrote in an op-ed for The Wall Street Journal. He has also said sanctions against North Korea and diplomacy with the country are ineffective and counterproductive as they give Pyongyang more time to develop its nuclear arsenal.

“The only diplomatic option left is to end the regime in North Korea by effectively having the South (Korea) take it over,” he said in a Fox News interview.

Bolton will be taking over from McMaster at a critical time when President Trump is expected to meet with North Korea’s leader, Kim Jong-un in April to negotiate an end to or restrictions on Kim’s fast growing nuclear weapons program.

  • He is a strong critic of the Iran Nuclear Deal

Just like Trump, Bolton is a critic of the Iran nuclear deal negotiated during the Obama administration. The agreement is aimed at stopping Iran’s nuclear weapon development in exchange for lifting existing sanctions. Earlier this year, Bolton suggested that efforts by the Trump administration to renegotiate the Iran nuclear deal with Iran and six other countries was a waste of time. He added that it is in the best interest of the U.S. to withdraw from the deal. Bolton also supports a regime change in Iran.

  • He might clash with Trump over Russia

Although Trump has continuously argued “getting along with Russia is a good thing, not a bad thing,” his newly appointed national security advisor has a different take on Russia. Bolton called Russia’s interference in U.S. elections “a true act of war, and one Washington will never tolerate.”

  • Bolton is no stranger to public service

Unlike many senior officials in the Trump administration, Bolton is not new to government service. He served as the assistant secretary of state for international organization affairs, the under secretary of state for arms control and international security affairs, and as U.S. ambassador to the United Nations during the Bush administration..

  • Bolton is opposed by Democrats, supported by Republicans

Within hours of the president‘s announcement, top Democrats in Congress came out against Bolton’s appointment. “The last thing we need is someone like John Bolton who embraces military solutions first and puts us all at risk,” Sen. Elizabeth Warren, D-Mass., Tweeted Thursday night.

Across the aisle, Bolton received praise and support from Republicans including Sen. Marco Rubio of Florida.

“I know John Bolton well, he is an excellent choice who will do a great job as National Security Advisor,” Rubio tweeted.

Regardless, the position of the national security advisor does not require Senate confirmation.