Editing M1 Abrams (section)

===Previous developments===
{{main|MBT-70}}
In 1963, the [[U.S. Army]] and the West German [[Bundeswehr]] began collaborating on a [[main battle tank]] (MBT) design that both nations would use, improving interoperability between the two [[NATO]] partners.<ref name="Jane's 1969" />{{sfn|Kelly|1989|pp=23-25}}{{sfn|Hunnicutt|2015|p=117}} The [[MBT-70]], or ''Kampfpanzer 70'' as it was known in Germany,{{sfn|Kelly|1989|pp=27}} incorporated many new unconventional technologies across the board. Conventional tanks of the time had a crew of four, with the driver located in the hull. In the MBT-70, the loader crewmember would be replaced by a mechanical [[autoloader]] and the driver would be located inside the [[CBRN defense|NBC-protected]] [[gun turret|turret]] with the other two crewmembers.{{sfn|Hunnicutt|2015|p=158}}{{sfn|Kelly|1989|pp=120}} Like the [[M60A2 tank|M60A2]] MBT and [[M551 Sheridan]] [[light tank]] then under development, the MBT-70 was armed with a 152&nbsp;mm [[gun-launcher]] that, in addition to firing conventional ammunition, would also fire the [[MGM-51 Shillelagh|Shillelagh missile]].{{sfn|Hunnicutt|2015|p=130}}{{sfn|Kelly|1989|pp=23-25}}{{sfn|Hunnicutt|2015|p=119}} A [[hydropneumatic suspension]] provided improved cross-country ride quality and also allowed the entire tank to be [[Enfilade and defilade|raised or lowered]] by the driver.{{sfn|Kelly|1989|pp=35}}

The United States team was led by [[General Motors]] while the German team consisted of a consortium of firms.{{sfn|Kelly|1989|pp=28}} The collaboration between the two teams was rocky from the start, with many cultural differences and disagreements about the design hampering progress.{{sfn|Kelly|1989|pp=23-25}} Germany favored a tank optimized for the terrain of central Europe while the U.S. attached importance to operating anywhere in the world.{{sfn|Hunnicutt|2015|p=118}} The Germans had reservations about the Shillelagh missile and developed a 120&nbsp;mm high-velocity gun as an alternative.{{sfn|Hunnicutt|2015|p=119}}<ref name="Jane's 1969" >{{cite book |editor1-last=Pretty |editor1-first=R. T. |editor2-last=Archer |editor2-first=D. H. R. |title=Jane's Weapon Systems 1969–1970 |publisher=B. P. C. Publishing |location=London |year=1969 |isbn=0-354-00516-2 |pages=191–192 |edition=1st |chapter= |url=https://archive.org/details/janesweaponsyste0000unse_m9k0}}</ref> Perhaps the most contentious disagreement, never fully resolved, concerned the measurement system to be used in drafting.{{sfn|Kelly|1989|pp=38}} Germany became concerned with the excessive weight of the tank.{{sfn|Hunnicutt|2015|p=142}} In light of growing costs, delays and overall uncertainty as to the soundness of the tank design,{{sfn|Hunnicutt|2015|p=140}} the United States and Germany ended their MBT-70 partnership in 1970.<ref name="Bonn and Washington split">{{cite news |last1=Beecher |first1=William |title=U.S. and Bonn End 7-Year Joint Effort to Build a Tank |url= https://www.nytimes.com/1970/01/21/archives/us-and-bonn-end-7year-joint-effort-to-build-a-tank.html |access-date=26 August 2018 |work=The New York Times |date=21 January 1970 |archive-url= https://web.archive.org/web/20180826113505/https://www.nytimes.com/1970/01/21/archives/us-and-bonn-end-7year-joint-effort-to-build-a-tank.html |archive-date=26 August 2018 |url-status=live |df=dmy-all}}</ref> The U.S. Army began work on an austere version of the MBT-70, named [[XM803]]. Systems were simplified or eliminated altogether and the unreliable autoloader was improved.{{sfn|Kelly|1989|pp=40}} These changes were ultimately insufficient to allay concerns about the tank's cost.{{sfn|Hunnicutt|2015|p=158}} Congress canceled the XM803 in December 1971 but permitted the Army to reallocate remaining funds to develop a new main battle tank.<ref>{{cite news |last1=Turner |first1=Bob |title=Congress Kills Tank Program |url= https://www.newspapers.com/image/332215721/?terms=xm803&match=1 |access-date=12 November 2021 |work=The Tampa Tribune |date=20 December 1971}}</ref>