US-Russian High-Alert Weapons
High-alert nuclear weapon commonly refers to a launch-ready ballistic missile armed with a nuclear warhead whose launch can be ordered and executed (via a nuclear command and control system) within 15 minutes or less. A definition of "high-alert" requires no specific explosive power of the weapon, but in general, most high-alert missiles are armed with strategic nuclear weapons with yields equal to or greater than 100 kilotons.
Virtually all high-alert, quick-launch nuclear weapons are possessed by the U.S. and Russia. It is important to note that no official totals for the number of warheads on high-alert, launch-ready status have ever been published by either of these nations. However, it is possible to arrive at reasonably accurate estimates based on historically known information and information obtained from various active and retired military sources.
It is commonly believed that most US and Russian land-based Intercontinental Ballistic Missiles (ICBMs) have been on high-alert status for decades, and are capable of being launched with only a few minutes warning.
A large variable in the calculation of total warheads lies in the question of how many Submarine Launched Ballistic Missiles should be considered at high-alert (these missiles can carry multiple warheads, so this is another variable). A leading expert on this subject, Dr. Bruce Blair, wrote in 2003 that the U.S. at that time kept 4 US Trident subs (24 missiles on each sub, with 5 or more warheads per missile) on "hard alert" status (see http://www.cdi.org/russia/264-2.cfm); these subs were kept in position to fire and thus all their warheads were considered to be on high-alert. Dr. Blair also has written that he believes Russia keeps 2 subs with 32 missiles and 92 warheads on high-alert.
The U.S. has 12 more Tridents armed with an additional 1152 warheads; Russia has another 576 warheads carried by the rest of its nuclear sub fleet. Thus there is quite a bit of room to increase the numbers of warheads on high-alert if you believe that some of these missiles are also kept ready to launch.
Tables 1, 2 and 3 give estimates of the current size of the high-alert nuclear forces in the US and Russia. The weapons yield (explosive power) is given in megatons (MT) of TNT equivalent.
Table 1 - US high-alert forces
aICBMs: 95% assumed alert rate
Table 2 - Russian high-alert forces
c 80% assumed alert rate23; 10 warheads per missile; 750 kT yield per warhead
Table 2 - US high-alert forces
h Total yield of US and Russian operational nuclear arsenals is approximately 2657 MT25, thus about 45% of the yield is on high alert.
All the numbers were taken from the High-alert nuclear weapons: the forgotten danger