1) Not all weapons systems are kept on 15 minute alert, so those cannot be launched immediately, including some sheltered bombers and mobile missile launchers.

1) Not all weapons systems are kept on 15 minute alert, so those cannot be launched immediately, including some sheltered bombers and mobile missile launchers. Other weapons systems, such as the Soviet (NATO reporting name) "typhoon" class submarines are purposely built to ensure that the enemy will not be able to rebuild. 2) A first strike may be intended to decapitate the leadership, decimate the enemy nuclear capabilities, destroy the entire army, or obliterate the whole country; the same goes for a second or third strike. It should also be noted that the Soviets implemented the "dead-hand" system so that any surviving installations would automatically retaliate even in the event of a successful first strike. 3) There are a variety of first strike scenarios, mostly involving SSBNs near the enemy coast, and stealth bombers since late in the cold war, as they give the shortest response window. Synchronizing a first strike would likely only be between one type of platform (i.e. all stealth bombers or SSBNs launching simultaneously); which is not too challenging. 4) First strike requires less than 15 minutes of notice, though even this may be too much. Soviets feared that the stealth bombers or a missile shield would encourage an American first strike exactly because the first would provide no response window, and the second would make any response futile. 5) Above. 6) Maybe. This all misses the basic point, which is that MAD made nuclear strikes even more pointless than they had previously been. Simply put, what is the point of destroying the enemy, and irradiating their territory (especially their most valuable assets) with a strike? Why would you put yourself at risk to achieve a goal of no benefit to you, except relieving paranoia, under MAD?