The Japanese or Nazis would not have stopped their invasion of other countries. The fact that so much of the genocide happened after the United States was involved does not mean it wouldn't have happened without our involvement. Remember the Japs attacked us first. And in many ways their atrocities were worse than Hitlers. Most only talk about the Nazis but both were horrific.
The Japs were far worse than the Nazis. However, they only had the opportunity to try and take over the Pacific because the British Commonwealth was busy in Europe. The Royal Navy, and virtually the entire militaries of Australia, New Zealand, and various other places, had gone to Europe. There was an enormous power vacuum, and they sought to take over. Those of us in the Pacific will forever be grateful for the USA for stepping in and preventing this. NZ ended up in the strange position that our own troops were in Europe, while US troops were based here.
However, if the Commonwealth had NOT been busy in Europe, there would have been no such power vacuum, and this Pacific war would not have started. Had the USA not supported Britain in 1940, they would have made peace with Hitler. Without a power vacuum to exploit, there would have been no Pearl Harbour.
And if I'm wrong, and the Pacific war had started anyway, it would have been stopped much faster, as the USA's full resources could have been devoted to that genuinely defensive theatre and they'd have been fighting alongside a full-strength Royal Navy and Commonwealth also. The Japanese could have never got past the Philippines.
Please, patriotic Americans, note that I am NOT blaming the USA for the Western war in Europe. I am blaming Britain and the Commonwealth - including my own country. The USA just aided and abetted them, and could have forced them to give up this foolish venture by choosing to withhold support.
The Japs may still have tried to take over continental Asia of course. Covering all the what-ifs could become a very long discussion but it's getting too off-topic so I'll stop.
Slewfoot has attempted to pre-empt that by establishing his own world government multiple times by using a leader/nation to conquer the other nations.I don’t see how pacifism would have blocked him from accomplishing his goal.
The more I've looked at WW2, the more I've come to believe that Hitler had no designs in the West other than reclaiming German territory lost in WW1. The evidence cited for Hitler having wider plans for the USA, Britain etc can often be traced back to Allied propaganda agencies, they are not necessarily real.
Hitler certainly had greater plans in the East - because he saw communism as a grave threat to Europe, and wished to knock out the USSR before they became unstoppable. The USSR certainly had very well documented plans for global domination - their ruling committee was explicitly called the "Communist International". The USSR was very overtly an attempt by Satan to establish a world government, and Germany was standing in opposition to this. To counter the USSR, Hitler would certainly have conquered much of Eastern Europe, all the way to Moscow, had he been left to his own devices. But given the extreme evil of Stalin's regime, and the obvious fact of their one-world-government intentions, I am not convinced that Hitler would have been worse. It may well have been better for Britain and the USA to have left the two dictators to fight each other, rather than helping the USSR take over all of Eastern Europe. Or even help Hitler defeat the USSR in exchange for receiving control of those countries in Eastern Europe they wished to keep free from the Nazis and negotiating provisions for the Jews in Germany - ie directly countering the evils of both Stalin and Hitler simultaneously (though that would not have been a pacifist position).
A lot is said about the Allies commitment to Czechoslovakia and Poland - but they clearly had no real commitment to either nation as they willingly handed both to Stalin. Britain declared war on Germany when it invaded Poland, but did not declare war on the USSR when it also invaded Poland days later. They were happy for both to be taken over by a dictatorial regime - they just wanted it to be the Communists rather than the Nazis. So the Allies actively supported Satan's world-government communist expansion plan.
Ultimately I think "Slewfoot" was at work directing the actions of all major parties involved in that war. Not just Hitler. Everywhere you look in that history you find evil.
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BUT
I'm not actually trying to debate the details of WW2.
I have only one point I am actually trying to make, and I'll say it clearly:
World War 2 does not prove that a pacifist position is wrong. The details are debatable, and there is
at least a reasonable possibility that a pacifist stance would have resulted in better outcomes. Which means that the "but what about the Nazis" argument does not disprove the pacifist position.
In answering the core question, we should stick to scripture, while paying strong attention to the opinions of early Christians who were more experienced in persecution than we are in interpreting that scripture. We cannot assume that the wars of our immediate past disprove the position taken by the early church.