Neville Chamberlain was in a tough position as the United Kingdom had pretty much disposed of their military in the aftermath of World War I. Their navy was certainly world-class, but the army and anything which could be used to stop Germany was basically non-existent. Ditto for the U.S. Army (which even had serious legislation going before Congress to completely disband the U.S. Army altogether and rely strictly on the state militias for national defense). The rest of the world was disarming at the time Germany was moving into the Rhineland and elsewhere.
Military intelligence was also miserable at the time, where Germany purposely inflated the numbers of their soldiers by marching the same units across prominent bridges (easily seen by observers)... only to ship them by train back to Germany to have them march again over the same bridge several times. Basically the UK & France thought Germany had many more soldiers involved in those early occupations than really was the case and something that might have been stopped simply by calling Germany's bluff.
I don't know if it is too late to do that with Putin's Russia or not... which I suppose is the question some are asking right now.