The United States Marine Corps:

The only branch whose primary mission includes all three: land, air and  sea. Marines protect the President and former Presidents, embassies around  the globe, nuclear weapon sites as well. Marines pride themselves on creating discipline, leadership and  motivation. Marines have deployed to every ocean and covered such diverse  operations as disaster relief in Guam to drug-interdiction along the  U.S. border. Operations other than war have come to dominate Marine  Corps operations that the Marine Corps has significantly expanded  traditional training resulting in the employment of new non-lethal  methodology. Marines work directly for the president Marines also is the only branch that works directly for the President  of the United States. (The others work for Congress). Therefore, the  Marines can be deployed within 24 hours anywhere around the world. Since the end of the Cold War Marines have increasingly been called  upon to respond to a growing number of unconventional crises around the  world. The Marine Corps' focus on littoral warfare, its forward  deployed presence, and rapid crisis response capability, make it the  natural force of choice to turn to... ... This has led some to call the Marine Corps the Nation's 911 force. Instead of large-scale conventional war (as the historical past), the  American military strategy has focused increasingly on low intensity  conflict and "military operations other than war". Correspondingly,  Marines find themselves conducting these operations with the other  services in a joint task force command.