I have always been curious as to what would have happened had the two gone to war. When germany annexed the czechs they added greatly to their war machine but taking over the sizable czech armored forces and factories. When you look at the difficulty that germany had taking over poland, just imagine that with a much smaller armor force that was not bolstered by the czech armored brigades. Also germany had hardly perfected the art of blitzkrieg, one could say that it was not really utilized tactically until the invasion of france.

One fact to also consider is that there were serious divisions within the german military prior to the czech annexation. Many high ranking officials in the german military had a coup planned for the moment that war was declared on the czechs, at which point they planned to arrest and assassinate hitler.

I also believe that the had the war taken place in 38, that the french would have continued with their Rhineland expeditionary force due to their alliance with the czechs, instead of pulling back to a defensive front like they did during the polish campaign. Germany would likely have been bogged down taking the czech fortifications in the Rhineland long enough to allow a british-french expedition to crush the german while they were relatively in a weakened state and before hitler had assumed godlike status amongst the population.

Loss of the Sudetendland made Czechslovakia's border undefensible.  

I was reading in Walther Spielberger's book on the T-35/T-38 tanks about how some Czech military officers were hoping to be absorbed into the Wehrmacht like the Austrian Army was.  Hence there was no sabotage of any equipment and the Czechs were eager to show their tanks and explain them to the Germans.

Agreed with 4v50 that the borders would have been tough to defend.

Look at a topographical map of Europe, and you can pick out the Czech Republic area:



You can see clearly on a smaller scale map that losing the mountain borders would make the rest of the country tough to defend:




Another factor to consider was the large German population that lived in the former Austro-Hungarian province of Bohemia for a long time.  The Germans living there may not have been Nazis, but they had been trying to come under Germanic rule for many years.




Of course, after the war, the Czechoslovaks solved the ethnicity problem by expelling the Germans.

https://en.wikipedia.org/wiki/Expulsion_of_Germans_from_Czechoslovakia