At the latter part of WW2, the Polish resistance made a great effort to drive away the nazis, hoping to avoid being occupied and ruled by Stalin’s already notorious regime.
Stalin wanted to get his hands on Poland, and so refused to supply the resistance with the weapons it needed, merrily letting them get slaughtered/arrested by the dozens. Only to further his own petty pleasures of being the absolute ruler of a few million more people.
Truman knew that Japan had been beaten, admittedly, Japan itself did not know it yet, but with the Soviets in the north, blocking access over,land, and the American navy blocking off access at all other borders (east, south and west are coastal borders), the Japanese government would not be able to acquire supplies/resources for the war machinery. So, really, all it would have taken for Japan to admit defeat and surrender, was a bit of patience.
Militarily, there was absolutely zero need for the murder of all those citizens with the atomic bombs that Truman did, apart from obviously striking fear in the hearts of every other population in the world, that the new boss in town possessed such very mighty weapons and wasn’t reluctant to use them on innocent people. Showing who was in charge.
And more recently, Bush2 (Dubbya) had zero reason to incade Iraq, because there were zero links to Osama Bin Laden. The trumped up excuses were a sham too: WMDs? (The only ones that were there dated back to the Iran-Iraq war and had been launched at Iran with the help of American targeting data).
But it had been long ago decided by the neo conservatives that a regime change would have to take place (be performed) in Iraq.
And the excuse of terrorism, to justify enslaving the population ever more, is also opportunism. As Macchiavelli wrote re any need a prince might have for a castle: “the only castle the prince needs, is not being hated”. To put that in my own words: the best defense against counterterrorism, is not committing terrorism.