When President-elect Donald Trump tapped Marine Corps. Gen. John F. Kelly to become his Homeland Security chief, it broke with a 15-year tradition of having lawyers and academics run the agency.

The newest mega-bureaucracy in Washington, DHS plays a pivotal role in securing our borders and creating a safe travel environment for all citizens coming into and going out of the United States.

According to Kelly, “the American people voted in this election to stop terrorism, take back sovereignty at our borders, and put a stop to political correctness that for too long has dictated our approach to national security.”

Here are three things to know about the agency the general has been tapped to lead:

Its creation was initially rejected by President Bush

When the Twin Towers fell on Sept. 11, 2001, federal lawmakers began to look at how a lapse in security made it possible in the first place.

The debate led several policymakers to believe the federal government wasn’t doing enough, leading Joe Lieberman and Arlen Specter to introduce a bipartisan bill asking for the Department of Homeland Security. President Bush initially shut down the idea, but the Senate continued to press for its approval.

Eventually, the 43rd president reversed his previous position and signed the Homeland Security Act.

It’s an umbrella agency with many purposes

After counterterrorism measures began in the early 2000s, Washington’s newest headquarters required several longstanding agencies to fold into their leadership directives — and a new one was created in order to secure the nation’s airports, the Transportation Security Administration.

Border Patrol, the Immigration and Naturalization Service, the Secret Service, the Coast Guard, and Customs Service all fall under the umbrella of DHS. Taxpayers chip in $41 billion to keep it running, hoping to ensure the safety of federal land, air and maritime spaces and prevent another tragedy on the scale of 9/11.

Its mission remains open for definition

As the threat of terrorism domestically ebbs and flows, Homeland Security has multiple ways it can educate and  the personnel at its agencies. The threat of climate change brings disaster response and recovery under a microscope, as DHS is responsible for training all FEMA workers on how to coordinate community relief amidst natural disasters, such as Hurricane Matthew.

It is also responsible for combatting cyber threats, and the agency must evolve along methods of hacking, as other realistic threats continue to develop.

As the leader of the third-largest Cabinet department, Gen. Kelly will be responsible for dictating the future direction of Homeland Security and provide the president with its intel from the field. That coordination will allow for the future of foreign policy to take shape in addition to providing domestic programs that make America safer.

“He is the right person to spearhead the urgent mission of stopping illegal immigration and securing our borders, streamlining [the TSA] and improving coordination between our intelligence and law enforcement agencies,” Trump has said of Kelly.