Between the Indian wars, there was a war with Mexico in 1846 and the Civil War, with "Company B" participating in both. During the Mexican War, the 1^st Infantry Regiment was sent across the border with General Zachary Taylor's Army and participated in the storming of Monterrey where they fought house to house in savage hand to hand combat. After Monterrey, the regiment was transferred to General Winfield Scott's command in 1847 and participated in the first amphibious landing in American history at Vera Cruz . Following the Mexican War, the regiment campaigned in the Texas area against the Comanches until the outbreak of the Civil War in 1861. Evading gathering rebel forces in Texas, the regiment initially fought in the Mississippi area and fought in one of the first battles of the Civil War at Wilson's Creek, Missouri in 1862. The 1^st Infantry then campaigned with General Grant against Vicksburg in 1863. Towards the end of the war, regiment was assigned garrison duty at New Orleans. the end of the Civil War found the regiment again fighting Indians. Company B, 1^st Infantry was consolidated in April, 1869 with Company B, 43^rd Infantry, Veteran Reserve Corps (originated on September21, 1866) and remained as Company B, 1^st Infantry. The company then campaigned against the Sioux in the 1870's and 1890's and against the Apache, led by Geronimo, from 1882 to 1886. After the end of the Indian wars the company was assigned to quell labor and mining disputes in California.The regiment was awarded 2 campaign streamers for the Mexican-American War and 4 streamers for the Civil War.

      Following the sinking of the USS Maine in 1898, war was declared with Spain and the 1^st Infantry was sent to Florida where it embarked on ships for Cuba. While in Cuba the regiment took part in the taking of the San Juan Heights and the capture of Santiago. In 1900, after occupation duty in Cuba, the regiment was prepared for shipment to China to help save foreigners threatened by the Boxer Rebellion. Instead, they were sent help quell the rebellion on the Philippine Islands, which had become a United States Territory during the Spanish-American War. The regiment fought in savage guerrilla warfare in the jungles of the Philippines from 1900-1902 and again from 1906-1908. The regiment was awarded 1 campaign steamer for the Spanish-American War and 1 for the rebellion in the Philippines (also known as the "Philippine-American War"). The regiment was not actively involved in World War I and was assigned in September, 1918, to the 13^th Division; being relieved on March 8, 1919 from assignment to the 13^th. It was assigned to the 2^nd Division on July 27, 1921, and reassigned on October 16, 1939 to the 6^th Division (later redesignated as the 6^th Infantry Division).

      The next war time engagement came during World War II, while still assigned to the 6^th Infantry Division. In mid-June 1943, the 1^st Infantry Regiment saw its first combat in the Toem-Wakde area of Dutch New Guinea when the 1^st and 3^rd Battalions, 1^st Infantry, moved across the Tor River into the vicinity of Maffin Bay, relieving the 20th Infantry. The 2^nd Battalion, 1^st Infantry, assumed responsibility for the protection of the bridgehead across the Tor River and the battalions were to remain east of the Tirfoam River to act as a reserve while the 20^th Infantry moved against Lone Tree Hill. The battalions of the 1^st Infantry, along with the 20^th Infantry fought a bloody battle with the enemy at Lone Tree Hill from June 21^st to the 30^th and secured the Maffin Bay area by July 12^th. With the end of the New Guinea Campaign on July 31^st, the regiment was shipped to the Philippines and assaulted Lingayen gulf on the island of Luzon. After a 2 week rest, the regiment made an assault landing at Sansapor, July 30^th, on the Vogelkop Peninsula. The 6^th secured the coast from Cape Waimak to the Mega River and garrisoned the area until December, 1944. The division landed at Lingayen Gulf, Luzon, in the Philippines on D-day, January 9, 1945, and pursued the Japanese into the Cabanatuan hills, January 17-21, capturing Munoz on February 7^th. On January 27^th, a special operations units also attached to the Sixth United States Army took part in the Raid at Cabanatuan. The division then drove northeast to Dingalan Bay and Baler Bay, isolating enemy forces in southern Luzon. The U.S. 1^st Infantry Regiment operated on Bataan together with the Philippine Commonwealth forces, cutting the peninsula from Abucay to Bagac. The division then took part in the Battle of Manila, shifting to the Shimbu Line northeast of Manila, took Mount Mataba, Mount Pacawagan, Bolog, Lane's Ridge of Mount Santo Domingo, and Kiangan. The 6^th remained with the Philippine Military forces in the Cagayan Valley and the Cordilleras Mountains until VJ-day. The 1^st Infantry Regiment received the "United States Presidential Citation" for its actions at Maffin Bay/Milne Bay and all members and veterans of the 1^st Infantry Regiment are permitted to wear the citation and the "Philippine Presidential Citation" which was awared for its actions between October 17, 1944 through July 4, 1945. The regiment moved to Korea during October, 1945 and remained in occupation there until the end of 1949. The regiment was awarded 1 campaign streamer for New Guinea and 1 for Luzon during World War II.

      In 1950, the Regiment was reactivated at Fort Ord, California as a training regiment for units being sent to the fight in Korea and remained in that capacity until 1956, when it was assigned to the United States Military Academy at West Point, New York. The 2^nd Battalion, 1^st Infantry was inactivated on May 15, 1958 at West Point, New York, and relieved from assignment to the United States Military Academy, being redesignated as Headquarters and Headquarters Company, 2^nd Battle Group, 1^st Infantry with its organic elements concurrently constituted. The Battle Group was assigned on March 17, 1958, to the 2^nd Infantry Division and activated on June 14, 1958 at Fort Benning, Georgia. The unit was again inactivated on May 10, 1963 at Fort Benning, Georgia, and relieved from assignment to the 2^nd Infantry Division. The unit was redesignated on September 10, 1965 as the 2^nd Battalion, 1^st Infantry, and assigned to the 196^th Light Infantry Brigade (Separate) and was activated on September 15, 1965 at Fort Devens, Massachusetts.

      In 1966, 2^ndBattalion, 1^st Infantry was shipped to Vietnam with the rest of the 196^th Light Infantry Brigade (Separate). The 196^th Light Infantry Brigade (Separate), known as "the Chargers", would fight for the next 6 years in Vietnam. Being designated a "separate" unit meant the brigade had no actual division assignment and it was initially deployed at Tay Ninh, where it began combat operations in the western area of the III Corps Tactical Zone. In April, 1967, the battalion, still assigned to the 196^th, was selected, along with the 1^st Brigade, 101^st Airborne Division and 3^rd Brigade, 25^th Infantry Division, to form a temporary division unit called "Task Force Oregon", where it was moved to the I Corps Tactical Zone. On September 25, 1967, Task Force Oregon became the 23^rd Infantry Division, referred to as the "Americal Division". It was composed of the original elements of the task force and added the 198^th, and the 11^th Light Infantry Brigades, even though the latter two organizations were still training in the United States. At the end of November, 1971, the 196^th was relieved from assignment to the 23rd Infantry Division and assigned back as the 196th Infantry Brigade (Separate), deployed to Da Nang to assist in port security duties. The brigade left Vietnam in June, 1972, as the last combat brigade to leave in Vietnam. The 2^nd Battalion, 1^st, Infantry Regiment, as part of the 196^th, was involved in major actions against the enemy throughout its tour in Vietnam and the regiment fought in 14 campaigns; including bloody 1968 Tet Offensive. The 2^nd Battalion, 1^st Infantry was awarded the "Valorous Unit Citation" for its role in Quang Tin Province in August, 1969 and 14 campaign streamers for its actions in Vietnam.

      Following its tour of duty in Vietnam, the battalion was sent to Fort Lewis, relieved from assignment to the 196^th Infantry Brigade (Separate) and assigned to the 9^th Infantry Division on July 21, 1972. On February 16, 1991, the Battalion became part of the 199^th Infantry Brigade (Separate) at Fort Polk, Louisiana, where it remained until inactivation in 1994. At that time it was relieved from assignment to the 199^th Infantry Brigade (Separate). On December 16, 1995 the Battalion was reactivated at Fort Wainwright as part of the 6^th Infantry Division (Light). Second Battalion was relieved on April 16, 1998 from assignment to the 6^th Infantry Division and assigned to the 172^nd Infantry Brigade (later redesignated as the 172^nd Infantry Brigade Combat Team). The unit was redesignated on October 1, 2005 as the 2^nd Battalion, 1^st Infantry Regiment. In August, 2005, 2^nd Battalion was deployed, along with the 172^nd (redesignated the 172^nd Stryker Brigade), to Mosul, Iraq in support of "Operation Iraqi Freedom". The battalion conducted counter insurgency operations aimed at securing the city of Mosul from an insurgency headed by the Al Qaida terrorist organization. After 12 months in Mosul, the 172^nd was preparing to return to its home at Fort Wainwright, Alaska when their deployment was unexpectedly extended. The 2^nd battalion, along with the entire 172^nd Stryker Brigade were subsequently sent to Baghdad, Iraq to quell rising sectarian violence. The 2^nd Battalion returned home with the 172^nd in December, 2006 after 16 months in Iraq. The unit was again awarded the "Valorous Unit Citation" for its combat participation in Iraq between August 15, 2005 and December 15, 2006.

      The battalion was again inactivated on December 16, 2006, at Fort Wainwright, Alaska, and relieved from assignment to the 172^nd Stryker Brigade. It was assigned on April 17, 2007, to the 5^th Brigade Combat Team, 2^nd Infantry Division, and activated at Fort Lewis, Washington. In February, 2009, the 5^th Stryker Brigade Combat Team, was ordered to Afghanistan, along with 8,000 Marines to be deployed in the southeast along the Afghan border. The brigade returned in July, 2010, and was inactivated and reflagged as the 2^nd Stryker Brigade Combat Team (SBCT) and its subordinate units were reassigned to the reactivated 2^nd SBCT.

      The only documented blemish on a heretofore outstanding war record of the 2^nd Battalion, 1^st Infantry was perpetrated by members of the 3^rd Platoon, Bravo Company in Afghanistan. The platoon was charged with the the formation of a "kill team" which staged three separate murders of Afghan civilians in Kandahar Province. In addition, seven soldiers were also indicted with crimes including drug use, impeding an investigation and attacking a private who alerted MP's during an initially unrelated investigation into drug use by members of the 3^rd Platoon. The overall legacy of the unit, in spite of this, documented transgression, is one of valorous soldiers performing a service to their country throughout the history of the United States of America.