The Strategic Air Command was the United States' first military force truly optimized and prepared for nuclear war. As a result, in the early days of the Cold War, SAC shouldered the lion's share of responsibility for deterrence-based policy. Bombers armed with nuclear weapons were kept on alert at all times so that in the event of an atomic attack on the U.S. or its forces and allies, those bombers would be ready to immediately sortie against their targets and avoid incoming strikes.
The problem with bomber forces has traditionally been that bombers themselves and their bases are both quite fragile (at least in terms of the kind of damage a nuclear weapon can deal out). Thus, no matter how 'ready' the bombers were, they still had to get airborne and then get a good distance away from the target area before an incoming weapon detonated in order to have any chance of surviving. Coupled with the relatively limited warning time of early surveillance and sensor systems, that meant that there loomed an 'exploitable delay' during which an opponent might reasonably believe they could destroy all (or enough) of the bombers on the ground to make a first strike an attractive option.
Curtis LeMay was not the type to rely on what his enemies (he didn't like the word 'opponent') might do. He didn't like relying on what they would do at all. Neither did most early nuclear planners. If it was possible to improve the situation unilaterally, that was always the preferred option. So they did.
The most obvious way to ensure that some bombers would survive a surprise attack on their bases was, of course, to make sure that at all times there were some aircraft which weren't at their bases. Not just away from their bases; they needed to be a credible threat all on their own, which meant that they had to essentially be flying in fully combat status. So that's what they did.
Operation Chrome Dome (along with its siblings like Operation Hard Head) was a plan under which fully armed and combat-prepared B-52 Stratofortresses would, several times a day, take off from their home bases and fly long patterns beyond U.S. borders. These courses were designed such that the bomber would, from as much of the course as possible, be able to immediately divert to and reach its target in the event of war. There were several operations of this type; Chrome Dome was the umbrella operation for a set of four general patrol routes, all of which were overtly threatening to the USSR without trespassing into hostile airspace. Bombers undertaking these missions were said to be on airborne alert.
One route, perhaps the longest, saw the B-52 take off from Sheppard AFB in Texas before flying to the tip of Maine, then skirting outside Canada over the Atlantic Ocean, turning northwest along Hudson Bay and overflying Thule AFB in Greenland, then turning southwest to fly down the Alaska/Canada border and then down the west coast of Canada and the US before turning eastward across Arizona and returning to base. This was known as the 'Northern Route.' This route was later modified to start at bases near the U.S./Canada border rather than Texas. One reason for this was that by their nature, these patrols involved flying with fully armed nuclear weapons onboard; the new routes minimized the amount of populated ground that the patrols passed over. The later 'Northern Route' did not make a circle of Canada, but rather flew out to nearly the eastern coast of Greenland before returning along nearly the same route; a complementary 'Western Route' that left the CONUS near Seattle would fly northwest along the coast and fly a track across Alaska and north before returning.
A third route involved crossing the Atlantic, passing over the Straits of Gibraltar, crossing Italy and flying a track around the inside of the Adriatic before returning by the same route. Finally, there was a 'miniature Chrome Dome' mission which simply orbited Thule AFB to 'keep an eye on things' as Thule was the most remote SAC presence.
The Chrome Dome flights advertised their presence, making radio reports of their positions (albeit not necessarily all that accurately) in order to let the Soviets know that armed U.S. nuclear bombers were abroad. During the Cuban Missile Crisis, in at attempt to unsettle the USSR, the Chrome Dome aircraft began to up their position reporting frequency 'just for emphasis.'
Chrome Dome was, perhaps inevitably, responsible for at least four nuclear weapon accidents. In 1961, a Chrome Dome B-52 experienced a decompression event that forced it to descend below 10,000 feet - this increased its fuel use significantly enough that it was unable to reach its next scheduled air-to-air refueling rendezvous, and it ran out of fuel and crashed near Yuba City, CA. Two nuclear weapons went down with it; their safety mechanisms prevented them from detonating. Crashes followed in 1964 (Cumberland) and 1966 (Palomares). Finally, in 1968, a B-52 over Greenland suffered a cabin fire. Unable to reach Thule, the crew ejected (with one casualty who was unable to escape the aircraft) and the plane crashed into the ice in North Star Bay. The weapons on board ruptured, and there was widespread contamination. This incident was compounded by an attempted cover-up by the US and Denmark, as Denmark had publicly denied that nuclear weapons were allowed in Greenland. Chrome Dome was terminated following this crash, and the SAC bomber force returned to 'ramp alert' procedures. As the SLBM and ICBM forces had come online, the risk of a splendid first strike had declined significantly.
- Sagan, Scott Douglas. The limits of safety: organizations, accidents, and nuclear weapons. Princeton Univ Press, 1995. 63,69,74-76, 169, 201 . Print.
- Larsen, Jeffrey Arthur. Historical dictionary of arms control and disarmament. Scarecrow Press, 2005. 17. Print.
Iron Noder 2010