When Germany remilitarized Rhineland during 1936 the WW1 Allied powers gained a casus belli against Nazi Germany. After a clear violation of a international treaty, there was no need for an preemptive strike. The cause for war against Germany was there, but the Western allies did not use it. So those circumstances really dont apply as example of preemptive forceful regime change conducted by an external power.
Of course this is a complicated issue and there is no simple answer, but how i see it. If you meddle with internal affairs of others without their consent the responsibility concerning the outcome lies with you afterwards.
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