United State Marine Corps (USMC) is a part of US Armed Forces, combined armed task force, trained for amphibious warfare. They are among one of the seven federal uniformed services of the US. They are a part of the US Dept of Navy as they train, and make use of the US navy infrastructure for logistical and transportation purposes. USMC has been a part of every armed conflict America has got involved in since its inception. USMC has around 203000 marines in active duty and around 40000 as reserve.
Their areas of responsibility include defending and capturing advanced naval bases and other land based operations, developing tactics and equipments for amphibious landing purposes and other duties as directed by the president of United States. Marines are basically expeditionary forces used in various quarters of ground combat at many instances. They play a vital role in the affairs of the national security because of their capabilities as an amphibious, expeditionary and air-ground combined arms task force.
USMC traces back to the days of the War of the American Revolution where 2 battalions of Continental Marines were raised for the first time and since then they have been a part of many battles ranging from the First Barbary War against the pirates of Barbary in the year 1801 to the present day Operation Iraqi Freedom. The longest of all the wars faced by the USMC was the Vietnam War, where they took part many important battles and also devised various non conventional techniques of counter insurgency against Viet Cong and also as military advisors for Republic of Vietnam Marine Corps.
I Marine Expeditionary force along with 3rd Infantry division of the US Army spearheaded the invasion of Iraq during Operation Iraqi Freedom in 2003 and they ended their role in the Iraq on 23rd Jan 2010 after handing over the responsibilities to the US Army.