From the moment the US detonated the first atomic bomb over Hiroshima on 6th August 1945 at 0815 it signalled the beginning of the Atomic Age. The 'Little Boy' uranium gun-type weapon was dropped on Hiroshima by the USAAF B-29 Enola Gay. At 0816 the bomb detonated, killing some 80,000, injuring 51,000 and destroying 42 square miles. The bomb also poisoned many more with lethal doses of radiation.

The threat of nuclear destruction kept the Soviet Union at bay until the formation of NATO on 4th April 1949. The first major doctrine was called 'Massive Retaliation' which involved US and later UK bomber retaliating with Nuclear bombers if the USSR crossed the border between East and West Germany or invaded a NATO country. This was to make up for the imbalance in conventional forces which favoured the USSR and because the US had an overwhelming superiority in Nuclear weapons at the beginning of the 50s. The concept was flawed because what constituted a large enough incursion to warrant "MR" was never really discussed. Would the US and NATO nuke the Soviets into the stone age for a small 5 mile border incursion? 

The launch of Sputnik in 1957 brought home to America the possibility that the USSR could launch ICBMs, which the USA did not possess at that time, and led to the scrapping of American reluctance to share nuclear information. It also gave the UK nuclear programme a shot in the arm, and helped to secure the US-UK partnership in NATO that had become strained after Suez.

The Anglo-US agreements led to US bombers being based in the UK from the early 1950s, a Polaris submarine base being built in Scotland and an early warning radar station in North Yorkshire.

MAD came in the 1960s with MacNamara. MAD was born with the realisation that the Soviets had, or would soon reach, parity in weapon numbers and bombers, making "MR" even more redundant than before.

MAD is based upon the idea of deterrence, Mutually Assured Destruction. referred to the concept of both knowing each others capabilities and knowing that any attack on each other would bring a devastating counter-strike, The argument was flawed because to the Soviets' deterrence didn't appear in their doctrine and the nuke was just another weapon in the armoury.

British doctrine stuck with MR until the Resolution/Polaris combination went live later in the 1960s. The French, in their unique way, decided to point some of their weapons at the US and ensure that in a possible nuclear conflict Washington got involved and didn't back out, they also pointed some of their weapons at West Germany, the idea being if the Soviet's did decide to attack they would use the weapons if the Soviet's looked like breaking through, or if the Americans didn't look like getting involved or West Germany decided to decline into one of its war-like earlier incarnations.

The Development of the Submarine Launched Ballistic Missile also provided additional deterrence in the event of one side pinpointing and destroying all the enemies weapons in a first-strike. The undetectable submarines could sit off an enemies coast and launch a devastating first or second strike, and as such were almost immune to detection, and combined with the near-unlimited range and endurance of a nuclear powerplant could patrol for months without having to surface, and thus give away their positions. More potency was added with the advent of MIRVs, Multiple Independent Reentry vehicles, which enabled a single SLBM or ICBM to carry multiple warheads along with decoys and strike several targets at once. Although projects to intercept and destroy these missiles were tested and developed none actually made deployment, short-range missile interceptors such as the Patriot system do not have the range to intercept a nuclear-armed missile far enough from its target to prevent significant or total destruction. Other projects include the famed 'Star Wars' system which as far as is known near made it into space and was banned in subsequent treaties by all sides. 

Thankfully, MR nor MAD were never put into use, although the pot did come close to boiling over during the Cuban missile crisis.

Various types of nuclear weapons have been prepared and stood ready to use in the event of war:

Notes: Two Versions, the SPL (self-propelled launcher) carries one ready to launch LANCE Missile. The LT (Loader-transporter) carries two LANCE missiles minus fins, which are stowed inside carrier. Withdrawn from service, mid-1990s. It equipped 50 Missile Regiment, Royal Artillery, which was commanded by HQ 1 (BR) Corps consisting of 15, 19, 36 and 51 Missile Battery, Royal Artillery. Each Battery had three launcher sections equipped with SPLs, two-assembly section with LTs and a single reconnaissance and survey section.