Some good points. Hitler seems to have been  surprised that the British took the invasion of Poland, partly because they  had been willing to allow the disgraceful dismemberment of Czechoslovakia the year before. He underestimated the role that honour might still play as a motivation for war, just as Germany did in 1914 in invading Belgium, at least in the mind of the British public who didn't know about British/French military coordination plans in the case of an invasion of France.  And the assassination of a foreign (future) head of state,  Franz Ferdinand, was a red line that the Serbian government (or elements of it) was willing to cross, in the expectation that the Russians would not allow them to suffer the consequences of it. (Hints of Assad/Putin.)