[magicsmoke]

Depends on what is considered a loss.

Bombers flying towards the political capital = launch the nukes.

Navy sunk and the enemy is setting up a blockade = maybe we'll go be north Korea instead of giving up existence here.

Both sides burn through all their high tech armaments and don't have enough to really keep fighting = truce for 3 years so we can build more shit for the next war.

[namelessoracle]

Depends on the country. A blockade for some countries would be basically death due to food imports being absolutely necessary. So they would probably start with lobbing nukes at the blockade which would likely escalate to nukes getting dropped on cities. If China for instance couldn't beat the US Navy and the Navy started blockading, a nuclear response on a carrier group starts looking attractive.

A country like US that can (for now) basically feed itself might have different lose conditions, though an effective blockade on a country like the US seems like it would require most of the world refusing to trade in any case.

There is also the egos of the various leaders at play. All it takes for example is a US president that decides he wont be the one who lost WW3 and decides that the other side will blink and let him/her get away with a first strike. For countries with unstable leadership this might even work! If you can take out for example Putin right off the bat, would whoever is next in charge want to get revenge for him if the Americans/Chinese/whoever reach out to the successor and offer them a sweetheart deal? after all accepting the deal means the world wont end....