What led to the creation of the department of homeland security?

 The 9/11 terrorist attacks that occurred in 2001.

Context/details:

The Homeland Security Act, which created the Department of Homeland Security, was passed in 2002, following the September 11, 2001 attacks by terrorists against the United States, which involved hijacking planes and flying them into the World Trade Center and the Pentagon.  The Department of Homeland Security describes its mission as ensuring "a homeland that is safe, secure, and resilient against terrorism and other hazards."

The Homeland Security Act of 2002 (Title I, Section 101), listed the top three priorities of the Department of Homeland Security as:

Also listed as part of Homeland Security's mission is that it will  "monitor connections between illegal drug trafficking and terrorism, coordinate efforts to sever such  connections, and otherwise contribute to efforts to interdict  illegal drug trafficking."

The Department of Homeland Security also acts "as a focal point  regarding natural and manmade crises and emergency  planning," and works to coordinate efforts between various agencies and law enforcement agencies  in order to achieve its security goals.  According to the Department of Homeland Security's own website, the Department of Homeland Security combines "22 different federal departments and agencies into a unified, integrated Cabinet agency."

in 550 b.c.e. cyrus the great, the leader of the persians, conquered the medes and united the iranian people under one ruler for the first time. cyrus became the first king of the persian empire and went on to establish one of the largest empires in world.