As has been said elsewhere, Nukes should be treated as a Defensive weapon and at the height of the cold war, the thinking was any war where Nuclear Launch was used, it was done so in a "If I'm going down, I'm taking you with me!" attitude. Most nuclear powers maintain a "Second Strike Only" policy for their nuclear arsenal (We will only launch our Nukes if we detect an inbound launch against us) and have done so for decades.
The U.S. is one of two nations that do not have a true second strike policy but maintain a limited First Strike Policy, that allows them to launch a first strike if the situation is desperate enough for them to do so. During the cold war in the 80s, the idea was that they would maintain conventional warfare against the Warsaw pact nations for as long as possible, but would launch tactical strikes (one or two missiles) if it looked like they would lose critical battles (generally, these launches would be against reserve forces that would turn the tide of an ongoing battle). Even then, the U.S. invested a lot of money in conventional forces to prevent this policy from being used in the first place (and while largely developed after the Hiroshima-Nagasaki bombings, the use of Nukes on Japan would be consistent with the limited first strike policy as the invasion of mainland Japan was expected to have a high level of casualties for allied forces. To give a perspective on this, the number of casualties was so high, that all physical Purple Heart medals (awarded to military personnel wounded in combat) award since World War II are from an order that the U.S. military placed as part of the build up to a conventional invasion of Japan... they haven't had to order the manufacture of new medals since the mid-40s. Needless to say, nothing has come close to doing that in an actual military conflict since.).
Oh, and incase you're wondering, the only other non-Second Strike policy nuclear nation is Israel, who's policy boils down to "We don't have nuclear weapons, and if we did, we certainly would keep it a secret and deny we have them, because we don't have them, and wouldn't make any public communications about our non-existent launch policy for our non-existent nukes, which we definitely do not have, because we don't have nuclear weapons. We certainly would never secretly maintain nuclear weapons, deny they exist at all, despite strongly hinting that we do have them so everyone else knows to back down... that would be totally irresponsible. But our current Nuclear policy is Second Strike Only Launch" (For an added bonus, have the report respond, "Sir, that's all well and good but my question was about the date of the IDF's family picnic day."). And if you didn't get that complicated boil down of the policy, the joke is that the Israeli Government officially denies that they have nuclear forces. However, even the most ardent supporter of Israel believes this is a blatant lie, not the least in part because the Israeli government has made it clear they do have them. Part of the reason for this is because regional politics are not favorable to Israel and that officially having nukes would spark further tensions with neighbors, but not having them is a giant gap in defenses when many of the other middle east nations are interested in getting nukes and seeing Isreal no longer exist. So officially they deny having them, but unofficially they let the world know they have them.