I will be honest, the verses that explain the length of the seven-year tribulation period are somewhat complex, but once understood, the first 3 ½ years of the tribulation period will be relatively peaceful, followed by the second 3 ½ years which will be filled with war and “war will continue until the end and desolations have been decreed” (i.e. until Jesus returns). The Seal, Trumpet and Bowl judgments outline in detail a global thermonuclear war that will occur in the second half of the tribulation period.