Doctrine had significantly shifted by the end of the war. The . Navy had followed in the footsteps of the navies of Great Britain and Germany which favored concentrated groups of battleships as their main offensive naval weapons.  The development of the aircraft carrier and its devastating utilization by the Japanese against the . at Pearl Harbor, however, shifted . thinking. The Pearl Harbor attack destroyed or took out of action a significant number of . Navy battleships. This placed much of the burden of retaliating against the Japanese on the small number of aircraft carriers. 
On September 11, 2001 the United States suffered thousands of casualties through an act of terrorism on the World Trade Center in New York City. The United States became involved in war with both Afghanistan and Iraq . The end of the first decade of the millennium saw the worst economic times since the Great Depression of the late 20s and 30s.
In 2008, Barack Obama, the first African-American President of the United States was elected and served two full terms. In 2016, Donald Trump defeated Hillary Clinton and became the 45th President.