Square Leg

Square Leg was a <a href="/facts/United_Kingdom/kuPAILt2">British</a> <a href="/facts/Ministry_of_Defence_(United_Kingdom)/9TG9a0ss">government</a> <a href="/facts/Civil_defense/xa73Rr3S">home defence</a> Command Post and field exercise which was held from 11 to 25 September 1980 and which tested the <a href="/facts/Transition_to_war/XssYkFJW">Transition to War</a> and Home Defence roles of the <a href="/facts/Ministry_of_Defence_(United_Kingdom)/9TG9a0ss">Ministry of Defence</a> and British government. Part of the exercise involved a mock nuclear attack on Britain; the exercise scenario of 150 nuclear weapons striking Britain, with "almost all" of these weapons having a yield ranging from 500 <a href="/facts/TNT_equivalent/nEQ5z8mp">kilotons</a> to 3 megatons and a resulting total yield of 280.5 megatons, was felt to be reasonably realistic, but the post-exercise report stated that a total strike in excess of 1,000 megatons would be likely. An increased ratio of <a href="/facts/Ground_burst/RI4T0jIp">ground bursts</a> to <a href="/facts/Air_burst/lWCThBuj">air bursts</a> was depicted to provide all the regional <a href="/facts/CBRN_defense/fKyUBaY0">NBC cells</a> with radioactive fallout challenges, with underwater bursts also being depicted. Furthermore, the scenario was altered from official assessments as these were highly classified and many participants did not have the appropriate clearance to see them.
Partial bomb plots were released for England and Wales and for Scotland, but not for Northern Ireland. While official casualty figures were not provided, <a href="/facts/Stan_Openshaw/2SbphQED">Stan Openshaw</a> and Philip Steadman produced an independent estimate of 29 million deaths (53 percent of the population) and 7 million seriously injuried (12 percent), with short-term survivors numbering 19 million (35 percent).
Square Leg was criticised for a number of reasons: the weapons used were exclusively in the high-yield megaton range, with an average of 1.5 Mt per bomb, but a realistic attack based on known Soviet capabilities would have seen mixed weapons yields, including many missile-based warheads in the low-hundred-kiloton range. Also, no targets in <a href="/facts/Inner_London/ahtJmMLS">Inner London</a> were attacked (for example, <a href="/facts/Whitehall/0GnuK4zH">Whitehall</a>, the centre of <a href="/facts/British_government/3zLlUWbx">British government</a>), though collateral damage from strikes on <a href="/facts/Outer_London/2whNdtxb">Outer London</a> targets and on <a href="/facts/Potters_Bar/6nmfkssz">Potters Bar</a> and <a href="/facts/Ongar%2c_Essex/T4w24rfN">Ongar</a> meant that much of the Inner London area was still destroyed; towns such as <a href="/facts/Eastbourne/xLjYtxNq">Eastbourne</a> were hit for no obvious reason. All government and military bunkers were assumed to have survived for exercise purposes, although <a href="/facts/Kelvedon_Hatch_Secret_Nuclear_Bunker/jnMFprut">Kelvedon Hatch Sub-Regional Headquarters</a> had difficulty in establishing regional control. The <a href="/facts/United_Kingdom_Warning_and_Monitoring_Organisation/eHDtLWY5">United Kingdom Warning and Monitoring Organisation</a> was not a "live" participant, with the strike data it would have provided instead being pre-recorded and played into the exercise as it proceeded, an aspect that was criticised by participants after the exercise.
The <a href="/facts/Lothian/FDv9KvXJ">Lothian Regional Council</a> refused to participate in Square Leg, and the exercise came under journalistic scrutiny after its details were leaked to the press, but otherwise, despite providing a "major boost" to the nuclear disarmament movement, it was not met with significant opposition in the way that the later <a href="/facts/Hard_Rock_(exercise)/ksjPDta6">Hard Rock</a> exercise would be.

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Square Leg