Intercontinental ballistic missile

An intercontinental ballistic missile (often abbreviated ICBM) is a weapons system that has played a role in several games across the Fallout series.

Background
An ICBM is a long-range ballistic missile. A typical single-warhead ICBM has a blast radius of several miles, and a fallout range of even further, depending on the explosive yield the warhead contains. ICBMs can be launched from missile silos or from mobile ground launch platforms or vehicles such as the missile carrier.

Fallout 3
In the Capital Wasteland, an ICBM launch terminal, launch codes, and facility can be found at Fort Constantine. The launch codes are for a Minuteman XI missile. The Delta IX rocket, while not originally designed and built as ICBMs, were converted to serve this purpose in 2034. One such example crashed just outside the Statesman Hotel in Washington, D.C. where it can still be found as of 2277.

Fallout: New Vegas
When the Great War broke out, 77 ICBMs were aimed at the city of Las Vegas. However thanks to Robert House's preparations, 68 of them were disabled or shot down in flight, sparing the city from direct strikes. The remaining 9 bombs landed in the desert around the city, with confirmed strikes at Black Mountain, Cottonwood Cove, Mesquite Mountains, and Nellis Air Force Base. Raul Tejada recalls that Mr. House's anti-missile defense systems could be seen shooting down ICBMs from as far away as Mexico City during his unmarked quest Old School Ghoul.

ICBMs play a much more prominent role in the add-on Lonesome Road and the overall history of the Divide. Several silos managed by the Commonwealth Defense Administration's Ballistic Defense Division were located in what would become the Divide, and when the Great War happened most of these missiles were not launched. Years later, the Courier delivered a device that activated some of these missiles while they were still sealed in their silos, resulting in the destruction of Hopeville and Ashton. As the NCR-Legion War reached its height in 2281, Ulysses, a former frumentarius who survived the destruction of the Divide, returned to the area to meet the Courier.

Luring the Courier back into the Divide, he sent them through the shattered landscape to see what they had done, and to meet him at his Temple, where most of the still functional Minuteman XI ICBMs were located. During the course of their traversal of the Divide, the Courier launched an ICBM from the Ashton missile silo, creating what Ulysses called the Courier's Mile. Once they reached his Temple, the Courier faced off against Ulysses, and through words or weapons beat him. They then had the choice of redirecting the missiles to hit NCR or Legion targets of their choosing or could attempt to cancel the launch. The weapons are seen in Lonesome Road endings.

Fallout 4
Pre-War, at the USAF's sentinel site located to the southwest of Boston, developmental work was underway on an unidentified 'heavy' ICBM intended to allow it to deliver multiple Mark 28 bombs (originally designed to be airdropped from strategic bombers) against a target. The missile itself is not seen in-game.

Behind the scenes
The general design of most of the ICBMs seen in Lonesome Road resembles a combination of the SM-65 Atlas and the LGM-25 Titan-II. Other missiles encountered seem to be Minuteman XIs.