A change in nuclear doctrine of one state doesn’t necessarily mean another will change their doctrine too. For example, Russia and India have a No-first-use policy, but the US and Pakistan do not; they reserve the right, in their doctrine, to use nukes whenever they see fit. The UK has a doctrine of first strike ambiguity, meaning that their adversary wont know whether or not they are willing to strike first until it starts raining MIRVs - or not.