A major Cold War intelligence issue for NATO was 'Is the Soviet Union adhering to arms control agreements or preparing a nuclear strike on the West?'

Spy satellites played a key role in answering this question - this thread reveals how much the West really knew... In July 1980 the National Photographic Interpretation Centre (NPIC) issued its latest 6 monthly review of Soviet nuclear assets and whether they were complying with arms agreements. This summarised satellite cover of the USSR by overhead assets.

In the 1980s the Royal Navy wanted to scrap its Wessex Helicopter force. Secret files reveal the staff battle in Whitehall by the RAF to prevent the Army taking over support helicopter forces . Read on for a Pinstripedline thread on interservice rivalry at its worst! The RN and RAF operated different variants of the Wessex - the RN version having a single engine. Used by the Fleet Air Arm, it carried out troop lifts, vertical replenishment and many other duties around the world. Over 100 were built and used from 1962 onwards.

The 15" guns outside of the Imperial War Museum in London are one of its most prized exhibits. They are a memorial to the 'big gun' ship. Yet the story of how they came to be there is little known but involves atomic weapons, the space race and lots of financial paperwork… In 1960 the Royal Navy scrapped HMS VANGUARD, the last 'dreadnought'. Made obsolete by the H-Bomb and changing nature of war, she was scrapped, not preserved - a sad but economically understandable decision.

"I present you the Soviet Ballistic Missile Submarine Red October" - A line from a superb movie. In reality the CIA knew far more about the Soviet TYPHOON class from the mid 1970s than Clancy could have guessed.

Thread on the CIA, Typhoons and spying on the Soviets... In 1975 whispers were emerging of a new Soviet class of SSBN, known as the TYPHOON. While Brezhnev hinted at its existence, the West knew little.

In briefings to US Senators, the CIA admitted "we have virtually no information on this"...

In 1983 the Royal Navy conducted a SECRET set of meetings to assess the performance of weapon systems across the Fleet. This is a short thread on internal RN analysis of just how (un)reliable its weapons really were in the aftermath of the Falklands War... Headline reading indicated that in 1982, Sea Dart had achieved 63% reliability, and Sea Wolf 65% in Op CORPORATE - the hope was that this would be improved for Sea Dart to 85% during 1983.

This is the Canberra bomber, made famous through over 50 years of operations. What is less well known is that in the 1950s TOP SECRET plans were made to use RAF Canberra's to carry out an audacious attack on Soviet shipping canals using Tall Boy bombs in the event of WW3... A key NATO concern on the outbreak of war was how to prevent Soviet Baltic Fleet ships and amphibious vessels launching attacks in Denmark and Northern Germany to deny the Baltic to NATO.

One way to do this was destroying the canals that would move these ships into place.

This TOP SECRET map from 1954 shows how the UK MOD planned for New Zealand to assume defence responsibility for UK and allied islands in the South Pacific in the event of WW3.

Short thread on how even in the 1950s, the UK saw NZ as a key partner in the event of global war. In the 1950s the UK still had a significant colonial footprint across this region, with a range of island colonial possessions and commonwealth responsibilities. It was assumed that if global war came, NZ would be asked to lead the defence of the region.

In 1984 the UK "Director General Intelligence", the most senior MOD Intelligence Official visited Washington. His trip report covers spies, espionage, ZIRCON, Typhoon SSBNs and sneaky submarine visits to the Barents Sea...

PSL Thread The DIS was the MOD core intelligence organisation, covering 'all source' analysis, overhead imagery and a range of military collection capabilities. Throughout the Cold War it enjoyed a very deep relationship with their US and Canadian counterparts.

In 1995 the US offered to lease the RAF the F16 jet to replace the Tornado F3 in the Air Defence role. This offer was quickly rejected by the MOD, for reasons that make fascinating reading. Thread on why 'leasing American' can be more expensive than 'buying British'. The Tornado F3 entered service in the 1980s, intended to provide long range air defence. It was well designed for its task - namely to be a missile carrier to shoot down incoming Soviet bombers / MPA over the Atlantic, and not as a dogfighter in Germany.

This is the V Force, designed to carry out nuclear strikes on every Russian city with over 100,000 people in it in the event of WW3. How did the UK decide its target plans, and how did it plan to defeat Russia in war?

Long PSL thread on early British nuclear war plans. In 1948 the British atomic weapons programme was underway. To understand how many weapons would be needed, and why, the Chiefs of Staff directed the MOD to come up with an analysis of how best to use nuclear weapons on the Soviet Union as part of an UK/US bomber offensive.

The assumption was that war would be no sooner than 1957 and that when it began, UK and US forces would conduct nuclear strikes on the Soviet Union at the earliest opportunity. No assessment was made of Russian nuclear capability.

In 1958 the MOD conducted a detailed study on the logistics stockpiles held by all 3 armed services for wartime use. Its findings were of great concern about the shortfall of stores, equipment and ammunition for use in general war. Short thread on why logistics win wars... The goal of the paper was to set out the wartime stockpile needs for all 3 services. It began by defining what was meant by conflict - a simple question but far more complex to define. For example - the UK used 'upper, midddle and lower' thresholds.

In 1977 the German SF Unit 'GSG' stormed a hijacked Lufthansa airliner in Mogadishu, rescuing all hostages. Two SAS participated using 'flash bang' grenades.

This led to demand for SAS CT training, and to buy their grenades including from the Iranian Government...

Thread! In the aftermath of the operation, the FCO received over 20 different requests for support from different countries, keen to learn about the SAS role in the rescue, get training and assistance and learn how to conduct hostage rescue.

In 1958 the JIC circulated an MI6 memo about the subversive threat of Egyptian school teachers in the ME/Africa region - in the eyes of British intelligence, they were a front for subversion and espionage!

Now pay attention 007 and read on for a most unusual MI6 memo... The Joint Intelligence Committee is the hub of British intelligence analysis, fusing reporting together to produce coherent assessment that informs policy making at the highest levels of the British Government. Any issue considered here is of major national importance.

It is June 1983, you have just been elected to Parliament and appointed a Minister in the MOD. Your staff provide you with an induction briefing pack, including a section on Counter Terrorism. This is the actual brief Ministers had on the role of the SAS & SBS in CT operations. Ministers were told that there was a permanent SAS team ready to conduct CT Operations in the UK. On the mainland this was known as OP MINSTREL, while in NI, it was OP GASTRIC.

This is a Soviet Typhoon class submarine. In 1989, when a Royal Navy Lynx had flares fired at it while 'observing' a Typhoon while on a secret intelligence mission in the Barents Sea.

Short thread on Soviet / UK naval incidents and interactions in the late Cold War era... By the late 1980s the Royal & Soviet navies had annual meetings to review incidents and attempt to define the 'rules of the game' for Incidents at Sea (INCSEA) to reduce tensions and the likelihood of a mistake.

In 1990 the Soviets met the UK delegation in London.

In 1982, the UK Government was sufficiently concerned about the threat of the Spanish attacking Gibraltar to issue covert 'Rules of Engagement' to UK forces setting out when they could open fire on Spanish forces, and brought the military to readiness for war.

PSL Thread.../ In the immediate aftermath of the invasion of the Falkland Islands, Gibraltar played a vital role supporting the UK task force. The airfield, naval base and stores were essential to support the Task Force. This piece of UK sovereign territory had to be protected at all costs.

This is the Mk3 LST, an RN landing ship In 1952 the Admiralty was tasked to develop plans to turn this into a 'catapult aircraft ship' embarking up to 4 Venom jets on a 'one use only' basis during WW3.

Thread on the 'forgotten aircraft carriers' of the 1950s. The CAM had its roots in 1941 where merchant ships carried a single 'one time only' Hurricane, launched by rocket catapult to provide air defence for a convoy to shoot down FW200 recce aircraft tracking convoys for German U Boats.

In 1947 HMS VANGUARD, the last British battleship took the King & His family to South Africa. TOP SECRET MOD files, only declassified in late 2025 reveal a very different story about how the ship came close to open mutiny - with MI5, the Admiralty and the King all involved... VANGUARD was launched by HRH Princess Elizabeth in 1944, and commissioned too late for WW2. In 1947 she was converted for service as a Royal Yacht to take the King to South Africa for the first visit by the Monarch. This was a high profile visit amid austerity of post war UK.

The photo was taken in Jan 47, just before she sailed.

In July 1990 the RAF Red Arrows visited the Soviet Union, providing displays in Leningrad and Kyiv. The trip report by the senior British Officer, Air Vice Marshal Pilkington is a fascinating insight to a time of hope, optimism and worry as the Cold War ended.

PSL Thread/ The visit was arranged initially to allow the Soviets to display in the UK, but became a solo effort. The hope to display over Moscow was cancelled for "technical reasons", so the itinerary was Leningrad and Kyiv, with a stop in Budapest on the way back.

In Dec 1987 Mikhail Gorbachev landed at RAF Brize Norton for meetings & lunch with British PM Margaret Thatcher, enroute to Washington.

While positive, he also directly attacked Thatcher for her sending missiles to Afghanistan.

A short thread on an incredible meeting. During 1987 the UK/Soviet relationship was tentatively improving, despite Cold War issues. Both leaders had a desire to improve their working relationship, so when the opportunity came, with Gorbachev flying to DC, the UK invited him to call in for a bilateral and lunch.

In May 1990, the RAF Chief of the Air Staff (CAS) visited Russia for defence talks with senior military leaders. His visit report is a fascinating insight into Russian fears of German unity, Soviet airpower and the "airborne ballet" display.
Short thread on his visit as latest The visit was intended to build confidence and links between senior military figures. It was seen overall as a success, marking openness in engagement, and with questions, often on military issues, answered. This was notable for being so unusual!