The thought of mutually assured destruction in the form of worldwide nuclear annihilation made leaders on both sides of the Iron Curtain squeamish. But, limited nuclear war, now there was a plan! Irradiating the Soviets just a little bit, you know, as a deterrent, was seen as the clearly superior option to outright ICBM volleys.
To that end, the US military began aggressively researching the use of very small, "tactical" warheads in the late 1960's. These micro-nukes would be capable of being delivered by conventional weapons systems like a Howitzer or set on a timer by Special Forces teams to turn any battlefield into an obliterated irradiated wasteland. And that's where the B-54 SADM comes in.
The Special Atomic Demolition Munition (SADM), which debuted in 1964, were suitcase-sized nuclear weapons designed specifically to stop any potential Soviet advance through Europe. NATO-member country or not, these portable nukes would act as deadly, radioactive barriers, not only denying entry but also demolishing resupply communications routes as well as destroying vital infrastructure such as dams, power plants, and bridges. Even allied infrastructure was fair game if it meant the Soviets wouldn't get their hands on it.
The idea was that Special Forces (in two-man teams, known as "Green Light Teams") would deploy behind enemy lines in Western Europe, typically somewhere with access to the ocean. One Green Light member would theoretically first parachute in, carrying the device itself, while the other member infiltrated the area via scuba. The parachutist would then set up the device while the diver provided support, then both would escape back into the sea for retrieval—via swift boat or submarine—before the 18 x 12 inch, 50-pound bomb detonated.
Despite the diminutive size, the bomb's W54 warhead delivered between 10 tons and 1 kiloton of TNT's worth of destructive force. The problem was, however, that these munitions also relied on inferior mechanical timers (which weren't affected by EMP blasts) that could detonate anywhere from 8 minutes early to 13 minutes late. And when you're running from a Hiroshima-sized blast, that 21 minute activation window is terrifyingly wide open. [Business Insider - Military Images - Wiki - 3AD]