War is unpredictable. The war may happen in stages and may see an escalation cycle. I think nukes will get mated with missiles and deployed and kept in readiness if the tensions rise.All nations that deploy nukes have dedicated crack protection teams deployed with every nuclear missile. In India during peacetime the airforce and army deploy only conventional weapons. Only in the event of imminent nuclear strike will the warheads and missiles be mated,the warheads are stored in super secure hardened locations protected by large numbers of troops 24x7.
On deployment the land based warheads will be provided with adequate protection till launch, possibly by paracommandos.
The airforce weapons will only be loaded onto an aircraft a few minutes prior to it taking off for a strike.
Only the naval missiles onboard ssbns are always loaded with nuclear warheads, these however can only be launched by a series of codes and keys held by three different individuals onboard the sub at any time. In the best tradition of the navy I believe anyone getting command of an ssbn shall be an impeccable lifelong patriotic naval officer and we have little to worry about theft from a submerged submarine on the high seas.
The scenario that nukes will be assembled and mated with missiles at the last moment is not a practical one. It is true only when possibility of war is low.