[Challenge] Make WWIII occur as early as possible with maximum casualties.

President Truman does not fire General MacArthur in 1951. Those who passionately hate communism uses the Korean War and supports MacArthur's case in using nukes in China. This forces the Soviet Union to most involve itself even more now militarily. Truman and all except some supports the "unconditional" victory and rejects the limited war mindset that he originally wanted.

Using nukes in China would would make all the Local chinese who had to recently experience the brutality of the Imperial Japanese during WWII, support Mao even more now. Keep in mind just how difficult it was for even the more militarily advance empire, Japan to deal with China. China would have been to much of a difficult place to occupy and wage full war with. Mao would have thrown as much people against the American as needed to force the Americans out. Mao's willingness to disregard human life would have helped him defeat the Americans by his Human Wave Tactic. America had 300 nukes she could have used against Mao. The war becomes extremely bloody in the Korean war but the War hawks pride in their new military technology and nuclear bombs are at new levels. China eventually is defeated but the Chinese rebellion continues to escalate the death toll of Americans. By the end of the war, casualty numbers would have dwarf the expectations of what would have happened had America invaded Japan during ww2 and not used its bombs.

In Europe, During the cold war, propaganda was used actively and the Soviet Union would have won this propaganda using what just happened in China. MacArthur also wanting to intimidate the Soviets does succeeds. In Europe, Great Britain, under the leadership of Churchill sense that the now intimidated and Paranoid Soviet leader, Stalin, will very soon position more soldiers in Europe in what would look like a preparation for invasion. Churchill executes Operation Unthinkable. But like the authors response to the operation unthinkable said "Our numerical inferiority on land renders it extremely doubtful we could achieve a limited and quick success, even if the political appreciation considered that this would suffice to gain our political object." In what looked like a blitzkrieg fails due to the massive size of the Soviet army. The Soviet Union executes there own operation and succeeds due to having a much larger population. The Soviet Union uses her nuclear arsenal in more important locations. France not yet having nukes loses out, Great Britain follows. The Neutral nations of europe afraid of the ussr fields as much people for the war as possible. America, uses its nukes in soviet occupied territories due to her inability to fly her bombers into Moscow. Stalin does not care so much about the bombed territories so long as its not Moscow. Stalin fortifies all the land areas leading to Moscow to the teeth. It would take years to reach Moscow. By then, USSR would have enough nukes. All western europe loses do the large numbers of the Soviets, but despite this fact, they're regularly bombed to push the soviets out.

Civil war happens at home(USA) parents are tired and everyone has had enough of the war but the leaders in America refuses to back down and will do all necessary tasks in suppressing the protests. Stalin, sends secret message to Mexico promising things and despite them ignoring and not being involved in ww2. Civil war is happening and a more divided America at home makes the whole thing worst. Stalin reaches to mexico and makes her realize her opportunity and declares war with America. America is no longer divided as they have an enemy to defeat. Mexico is horribly defeated by those who wants revenge and fragments Mexico. This is used by the American leadership to give a much better reason to continue there fight against the soviets. Americans, now no longer divided, are more unified to fight against the Soviets, military war productions of America continues to grow and larges fleets of Americas navy is sent into europe, the Soviets are aware of America coming and does everything her power to make American penetration into liberating the more important western european countries so difficult it would destroy American morale.

By the end of the day, the total casualties would amount to hundreds of millions more of this would be coming from Asia and Europe. I would hate to be in that world tbh.

Easy. In 1950 both the US and Russia intervene in the Korean war, this pisses off Stalin, who is more drunk than usual, he commands the firing of their nukes, first tested the previous year, on the United States. Knowing they are about to be decimated, in one last act of prideful defiance, Truman (a nukehound at this point) fires American nukes on every Soviet ally. Finally, ensues widespread chaos and the near-destruction of mankind. WWIII.

I know this is forbidden but it is possible for WWIII to happen in 1946