Originally formed during World War I in France as part of the American Expeditionary Force, the Second Division was unique in that it contained both Army units -the 9th and 23rd Infantry Regiments in the Third Brigade- and Marines -the 5th and 6th Marine Regiments, in the 4th Marine Brigade. The division was also commanded by Marine Corps generals twice during World War I, the only time in American history when Marine officers commanded an Arny division. One of these Marine generals, Major General John Archer Lejeune (for whom the Marine base Camp Lejeune is named) would lead the division from July 1918 until it returned to the United States in 1919. The Second was committed to battle in the spring of 1918 despite French evaluators rating it as unprepared for combat; it was thrown into the Battle of Belleau Wood in a desperate attempt to halt the German offensive's drive on Paris, and continued on to help break the longstanding stalemate of the Western Front in the Chateau-Thierry campaign that followed. After General Lejeune assumed command, the division went on to win victories at Soissons, Blanc Mont, and finally the Meuse-Argonne offensive. Following the armistice, the Second Division took up occupation duties in Germany until April 1919; it returned to the United States in July 1919. The division was awarded the Croix de Guerre three times for gallantry, which entitles all members of its component units to wear the fourragere. This forced a change to the dress uniform for Navy corpsmen assigned to the Fifth and Sixth Marines; a shoulder strap was added to the uniform so that they could wear the fourragere, the only Navy personnel allowed to do so.

The Second Division was one of three Regular Army divisions preserved intact after the war and was based at Fort Sam Houston, Texas. As part of America's mobilization prior to World War II, the division was the first to reorganize from the "square" (two brigades with two two-battalion regiments each) structure to the "triangular" structure, which gave the division three regiments with three battalions each. For the next three years the division would be engaged in training and maneuvers before shipping out to England in October 1943, engaging in more training, and finally landing at Omaha Beach on D-Day plus 1, July 7 1944. The division was part of the exploitation force that took advantage of the St. Lo breakout, and subsequently took part in the siege of Brest, which lasted until September 1944. The Second was peripherally involved in the Battle of the Bulge, and later advanced into the Rhineland; it would continue further into Germany, taking Gottingen on April 8, 1945, Merseburg a week later, and Leipzig on the 18th of April. After withdrawing its pickets from across the Mulde River, the division moved 200 miles to positions on the Czech/German border, from which it advanced to take Pilsen on VE Day.

Returning to New York on July 20, 1945, the Second moved to Camp Swift in Texas and began training for its role in Operation Coronet, the projected final invasion of Japan. When Coronet was canceled in March of 1946, the division moved instead to its new home base at Fort Lewis, Washington, where they engaged in arctic, air transport, and amphibious, and maneuver training.

The Second Division was alerted for movement when the Korean War broke out, and arrived at Pusan on July 23, 1950, the first unit to arrive straight from the United States. At first the division was used in a piecemeal fashion, but on August 24th it was committed to action as a unit, relieving the 24th Division at the Naktong River line. The North Korean army struck hard a week later, launching a desperate human wave attack on August 31, and over the next sixteen days the Second committed its office clerks, bandsmen, technicians and supply clerks to the defense and eventually prevailed. The Second was also the first unit to break out of the Pusan Perimeter, and would lead the Eighth Army on its drive to the Manchurian border. It would get to within fifty miles of the border when the Chinese attacked in November 1950, driving back the U.S. and ROK forces. Again the Second was called on; this time it would be tasked with the vital mission of covering the rear and right flank of the Eighth Army as it retreated back to South Korea. The bitter fighting in the Arctic cold cost the division a third of its strength in the battle of Kunu-ri and the subsequent retreat through the "Gauntlet", including the attached Turkish Brigade. After integrating replacements, the Second returned to the line, blunting the Chinese winter offensive at Wonju on January 31; in turn, the division went on the attack in February 1951, reinforced by the French battalion, and would play a prominent role in smashing the Chinese Spring Offensive in April and May, for which actions it was awarded a Presidential Unit Citation. Alternating periods of combat and rest followed until the division was withdrawn for good in April 1954 and redeployed to Fort Lewis in August 1954, four years after its first elements had arrived in Korea. During its first tour in Korea, the Second Division suffered over seven thousand combat deaths, the highest total of any Army division in this century.

The Indianhead Division remained at Fort Lewis for only two years before moving to Alaska in August 1956. It was to be deactivated in November 1957, but in the spring of 1958 was instead reconstituted at Fort Benning with personnel and equipment from the 10th Mountain Division, which had been withdrawn from Germany. The Second remained at Fort Benning as a training division until March 1962, when it was transferred to the Strategic Army Corps and underwent additional training to improve operational readiness. In July of 1965, its units were transferred to the 1st Cavalry Division (Airmobile) at the same time that the 1st Cavalry Division in Korea was reflagged as the Second Infantry Division. The Second Division has remained in South Korea since that time as the main American ground force in South Korea, although since 2005 only one mechanized brigade (plus artillery, aviation, and divisional support assets) has actually remained in the ROK, with the rest of the division based at Fort Lewis. Interestingly, the division contains 1,100 KATUSA augmentees, South Korean soldiers who are part of the division.

As part of Operation Iraqi Freedom, the 2nd Brigade Combat Team (BCT) of the 2nd Infantry Division deployed from Korea to Iraq in August 2004, initially being assigned to the area around Fallujah. but later being moved to Ramadi, where in an interesting twist on the unit's history, it was attached to the First and Second Marine Divisions successively. This entitles soldiers from the 2/2 BCT to wear combat patches from either the 2nd ID or one of the two Marine divisions. The 3/2 BCT in was deployed to Nineveh in June 2006; the 4/2 BCT was deployed in April 2007. The 2/2 BCT returned to Iraq in October 2006, this time attached to the 1st Cavalry Division in Baghdad.

In addition to its Iraq deployments, the division also sent the 5/2 BCT to Afghanistan in February 2009.