Editing M1 Abrams (section)

===120&nbsp;mm gun M1A1===
[[File:Anniston Army Depot workers perform reset work on the turret of the M1 Abrams tank in 1989.jpg|thumb|left|M1 Abrams tanks being refurbished at the [[Anniston Army Depot]] in 1989]]

A number of considerations had led the service and its contractors to favor the Army's standard M68 105&nbsp;mm gun over Germany's 120&nbsp;mm [[Rheinmetall Rh-120]] [[smoothbore]] gun for the XM1. To begin with, the 105&nbsp;mm gun was "the smallest, lightest, and least costly gun adequate for the job."<ref name="Bolte=nb">This is the testimony of Brigadier General Philip L. Bolte, Deputy Commanding General of the U.S. Army's Testing and Evaluation Command, before the Investigations Subcommittee of the House Committee on Armed Services in April 1978; ''Army Reprogramming Request No. 78-14 P/A, FRG Smooth Bore 120-MM Gun and XM-1 Tank'', 95th Cong., 2d Sess., p. 30.</ref> Indeed, new kinetic energy ammunition for the weapon then under development by the Army promised to extend the gun's usefulness well into the future. And because the Army's other tanks, the M60 and the upgraded [[M48 Patton|M48]], as well as the tanks of virtually every other NATO nation, used the 105&nbsp;mm gun, mounting that gun on the XM1 promised to increase standardization within the alliance. Moreover, the continuing development of the new ammunition for the XM1 automatically upgraded every other gun in NATO. For all of these reasons, the XM1's development proceeded "on the assumption that the 105&nbsp;mm gun would probably be the eventual main armament."<ref name="Bolte=nb"/>{{sfn|McNaugher|1981|p=38}} The tripartite British—American—German gun trials of 1975 produced a general agreement in the U.S. Defense Department that at some future point, a 120&nbsp;mm gun of some design would be added to the XM1. Apparently anticipating this, Chrysler and GM had both made changes to their tanks during development to make them compatible with a variety of main guns.{{sfn|McNaugher|1981|p=40-45}} In January 1978, the [[Secretary of the Army]] announced that the Rheinmetall 120&nbsp;mm gun would be mounted on future production versions of the XM1. This decision established the requirement for a separate program for the XM1E1 (with 120&nbsp;mm gun) so that the XM1 program could continue unimpeded.{{sfn|Information Spectrum|1983|p=B-7}}

About 5,000 M1A1 Abrams tanks were produced from 1986 to 1992 and featured the M256 120&nbsp;mm smoothbore cannon, improved armor, consisting of [[depleted uranium]] and other classified materials, and a [[CBRN]] protection system. Production of M1 and M1A1 tanks totaled some 9,000 tanks at a cost of approximately $4.3 million per unit.<ref name="pogo.org"/>

In 1990, a [[Project On Government Oversight]] report criticized the M1's high costs and low fuel efficiency in comparison with other tanks of similar power and effectiveness such as the Leopard 2.<ref name="pogo.org"/>

As the Abrams entered service, they operated alongside M60A3 within the U.S. military and with other NATO tanks in various [[Cold War]] [[List of NATO exercises|exercises]] which usually took place in Western Europe, especially [[West Germany]]. The exercises were aimed at countering Soviet forces.{{citation needed|date=March 2023}}

Adaptations before the [[Gulf War]] (Operations Desert Shield and Desert Storm) gave the vehicle better firepower and Nuclear, Biological and Chemical (NBC) protection.{{sfn|United States General Accounting Office|1992}}