The 2nd Infantry Division ("Indianhead") (2ID or 2nd ID) is a formation of the United States Army

United States Army

The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

. Its current primary mission is the defense of South Korea

South Korea

The Republic of Korea , , is a sovereign state in East Asia, located on the southern portion of the Korean Peninsula. It is neighbored by the People's Republic of China to the west, Japan to the east, North Korea to the north, and the East China Sea and Republic of China to the south...

 in the initial stages of an invasion from North Korea

North Korea

The Democratic People’s Republic of Korea , , is a country in East Asia, occupying the northern half of the Korean Peninsula. Its capital and largest city is Pyongyang. The Korean Demilitarized Zone serves as the buffer zone between North Korea and South Korea...

 until other American units can arrive. There are approximately 17,000 soldiers in the 2nd Infantry Division.

The 2nd Infantry Division, unlike any other division in the Army, is made up partially of Korean soldiers, called KATUSA

KATUSA

KATUSA stands for Korean Augmentation To the United States Army. Qualified Korean draftees who demonstrate a high level of English fluency and aptitude via a standardized written exam may apply for a KATUSA slot...

s (Korean Augmentation to US Army).