Well that's the figures given in Revelation, the first 4 seals kill 1/4 of the population of earth then the 6th trumpet kills another 1/3 (so about half the population before the seals total), no death tolls are given anywhere else, but it's likely to be substantial.
But things keep happening and there are people still experiencing them so.. yeah, the war itself is not the end only "the beginning of the end".. and I think more likely, the first 4 seals are used to set up a "new normal" global government, so recovery from that war takes place to some degree, there may even be a gap of years. Revelation 6 gives no time markers for the first 4 seals, so it can be before the 70th week, the only time marker given, is the 6th seal, which per Jesus in Matthew 24, happens after the midpoint of the 70th week.
the first four seals however, I do believe point to a world war.
the 4th seal mentions beasts of the earth. People think "wild animals" but when Revelation talks about beasts, it's gentile empires, or the rulers of them.
So 4th seal, involves gentile empires going to war and killing 1/4 of the people on the planet through war, famine, and disease resulting from it. Whether this war uses nuclear or biological weapons is speculative, but I think it likely given the death toll of it.
but 3/4 survive.. and rebuild, and the wrath of God comes later (Revelation 6:17)
so the big potentially nuclear war?
not the end.
just the beginning.