Square Leg was a 1980 British government home defence Command Post and field exercise, which tested the Transition to War and Home Defence roles of the Ministry of Defence and British government. Part of the exercise involved a mock nuclear attack on Britain. It was assumed that 131 nuclear weapons would fall on Britain with a total yield of 205 megatons (69 ground burst; 62 air burst)[1] with yields of 500 KT to 3 MT.[2] That was felt to be a reasonably realistic scenario, but the report stated that a total strike in excess of 1,000 megatons would be likely.
Mortality was estimated at 29 million (53 percent of the population), serious injuries at 7 million (12 percent), and short-term survivors at 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 megatons 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 Inner London were attacked (for example, Whitehall, the centre of British government), though collateral damage from strikes on Outer London targets and on Potters Bar and Ongar meant that much of the Inner London area was still destroyed;[3] towns such as Eastbourne were hit for no obvious reason.[4] The Lothian Regional Council refused to participate in Square Leg,[5] but otherwise the exercise was not met with significant opposition in the way that the later Hard Rock exercise would be.
Operation Square Leg was one of the exercises used to estimate the destructiveness of a Soviet nuclear attack in the 1984 BBC production Threads.
The following table shows the hypothetical pre-strike event list drawn from the national Main Event List for Square Leg, testing the Transition to War stage.[6]
| 15 August | Cabinet instructs all departments and specified authorities to review their plans for Transition to War. | |
| 16 August | Fuel rationing imposed. | |
| 27 August | Government requests preparations to be made to remove art treasures. | |
| 31 August | Industrial unrest and large-scale activity by extreme left- and right-wing parties. | |
| 1 September | Considerable cross-Channel movement into the UK by expatriate families on a self-evacuation basis. | |
| 7 September | Prime Minister Speaks to nation on TV/radio. | |
| 9 September | Secretary of State authorizes power of direction over British Airways | |
| 11 September | Prime Minister again speaks to nation. | |
| 12 September | ‘Protect and Survive’ instructions issued through the media.Cabinet approves Queen's Order 2. Directed food buying (by government departments, police, and military services, etc.) Noticeable rundown of industry. Local authorities, MP's, police and the services swamped with offers of help in forming some sort of civil defence/Home Guard organisation. | |
| 13 September | Prime Minister again speaks to nation.Panic food buying breaks out in some areas. | |
| 15 September | General Alert and war declared. Fighting breaks out on continent. Conventional bombing on defence related targets in UK. Public reaction to bombing is mixed... those living in high-rise flats and in areas generally thought to be obvious targets leave home quickly. Industry seriously affected. Schools close in afternoon. | |
| 17 September | Government authorises local authorities to staff their wartime headquarters.Public passenger transport operating at fifty per cent of capacity. Government orders manning of headquarters in the Regions. | |
| 19 September | Attack Warning Red 11.55 am. Nuclear strike starts at 12.01 pm. 205 Megatons total fall on the UK. 131 nuclear weapons (69 ground burst; 62 air burst). Mortality at 29 million (53 percent of the population), serious injuries at 7 million (12 percent), and short-term survivors at 19 million (35 percent). |
The 'survival' stage details the events that occurred post nuclear attack, based on extracts from the War Diary of Warwickshire County that was used during Square Leg.
| 20 September | Daily food requirements: 680,700 rations. Eighteen thousand people (in refugee camps) suffering third degree burns. Isolated reports of refugees leaving West Midlands area. | |
| 22 September | Casualty aid points swamped. Hospitals and improvised hospitals full.Decision taken to conserve police strength with a view to deployment of Police Support Units later. | |
| 23 September | Commence mass advise to achieve public order.Reappraise triage. Request medical aid from military. | |
| 24 September | Establish additional casualty aid points close to existing where possible. Commit to home nursing casualties who will probably die. Commence grave-digging operations. (Transport) Remove dead from casualty aid points; remove dead from damaged areas as radiation levels permit.Fire situation in county under control. | |
| 25 September | Identify rationing levels of food and water. Identify additional rationing requirements for workers. Flow of refugees from the West Midlands is indicated; 31,000 to North Warwickshire, 12,000 to South Warwickshire. | |
| 27 September | Casualty figures Rugby area is indicated 30,000 plus estimate, Nuneaton area 17,000 plus. Large numbers of persons suffering first stages of radiation sickness. Arrange for establishment of decontamination units. Consider variations to law- liaise with police. | |
| 28 September | Estimate 100,000 plus refugees coming from West Midlands- most injured/shocked/irradiated. Consider disinfection in Rugby/Coventry area to avert disease. Liaise with military for aircraft for spraying. Control of refugees in the west of the county impossible at this date. (Via Wartime Broadcasting System) advise public on measures being taken to alleviate rioting and looting. Produce advice to encourage 'Good Neighbourly' behaviour towards refugees. Advise public with regard to disposal of dead bodies. Advise populace not to leave their area. | |
| 29 September | Numbers increasing at casualty aid points, priority being given to savable under- thirties. Anticipate refugee figures to be 200,000 plus. Further requests to Sub- Regional HQ or additional food; SRHQ (sub regional headquarters) directive received- conserve food. | |
| 30 September | Arrange collection of food from Buffer Depots. Liaise with police and military for convoy guards. Food to be held and guarded in district stores. Deaths becoming a serious problem, liaise with transport and works for speedier removal of bodies from casualty aid points. Advise public on action to be taken re looting- particularly theft of food. Call for volunteers to assist with transport and work tasks. | |
| 31 September | Notifications from SRHQ; twenty-five per cent food requirements for refugees to come from local Buffer Depots. Police Support Units established and deployed to areas where refugees are known to be located. Consider establishment of interim police control in known trouble areas, | |
| 1 October | Feeding to commence at 1800 hrs. Calorific content of meals will be six hundred + one pint of water (non-workers), 800 + two pints of water (workers). Meals provided for infant feeding totally inadequate, request additional supplies. Known casualty figures 37,000; seriously injured 67,000. Radiation sickness entering the third stage. Disease control absolute priority. All Essential Service Routes cleared. Identify and prepare additional burial resources. Advise public on location and times Feeding Centres will be open, safe routes to them (and) emphasize subsistence level of feeding in operation. |
The 'recovery' phase reports are drawn from the Gloucestershire log of requests for military support.
| 3 October | Request for air reconnaissance at Little Rissington food depot. | No response. |
| Provide armed troops to assist police at ten locations on M5 Motorway. | Thirty men deployed. | |
| Provide coils of barbed wire. | Barbed wire requested. | |
| Provide armed troops to assist troops at Gloucester to: (a) quell disturbance involving eight thousand persons. (b) guard a food warehouse at Hare Lane. | Twenty-five troops dispatched. | |
| Provide ambulances, trained first aid personnel and medical supplies. | No ambulances, trained first aid personnel or medical supplies available. Some vehicle only drivers. | |
| Provide armed troops to assist police with law and order problems at Cirencester, Cinderford, Lydney and Newnham. | Thirty men made available for Cirencester. Due to radiation hazard, (it is) not considered effective to send armed parties into other areas at this time. | |
| Provide armed guards to secure MAFF warehouse. | County Military HQ requested AFHQ 7 to provide assistance from east of country due to radiation levels. | |
| 4 October | Provide assistance to police at Gloucester to deal with law and order problem. | Fifteen men from Hare Lane detailed for this task. |
| Secure and guard a food warehouse at Cirencester. | Twenty armed men dispatched from Innsworth at 0930 hrs. | |
| Provide guards at twelve food supply and cooking centres throughout the country. Provide escorts on ten food supply vehicles. | Five armed guards provided at each location. Two armed guards provided for each vehicle. | |
| Assist police to prevent hostile crowd gaining access to Gloucester District Wartime HQ. | Twenty armed men made available. | |
| Assist police at GCHQ (Government Communications Headquarters in Cheltenham) which is under attack by looters and refugees. | Two mechanized platoons dispatched at 1400 hrs. | |
| Accommodate five thousand homeless at RAF Innsworth. | Cannot accommodate at RAF Innsworth but could take four thousand two hundred at RAF Quedgely. Vehicles available at Aschurch, but no drivers or fuel. | |
| Provide hygiene and sanitation teams and equipment at Cheltenham. Provide rodenticides and disinfectants. | Unable to assist. | |
| Provide security patrols and barbed wire at Special Rest Centre at Stroud for suspected disease-carrying refugees. | Two platoons dispatched to Stroud. No stocks of barbed wire available. | |
| Provide assistance to Ministry of Agriculture officers who have been prevented by hostile crowd from arranging the dispatch of food from a market garden. | 1630hrs. Wessex helicopter and twelve soldiers sent to scene. |