There is one major factor that is not taken into account here. Yes the Czechs had a defensive line but this was in the Sudetenland which was peopled with 3 million Germans who wanted the area to be annexed to the Reich. This was the pretext used by Hitler. Bohemia and Moravia are like a natural mountenaous fortress belt surrounding the Republic. By annexing this region , Germany took most of its defensives and that one point that was neglected at Munich by England and France. It was a key aspect of Germany's policy. The Munich compromise said that all Sudeten territories which where peopled with at least 50% Germans would be part of the agreement. Some of these guys had been militating for this since the 20s and they welcomed the Germans as liberators. There is no way the Chechs could have opposed this annexion alone.
When Germany finally invaded what was left of Chechoslovakia in March 1939 there were in facts a few fights and 132 Germans lost their lives.

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