Ok then Czech available manpower was 1.2 to 1.5 milion depending on
sources
It was rather their mobilization potential, not manpower. See, if Poland having 35 million
population, had a manpower of about 9 million, out of which 7 were fit for military service
and the mobilization potential was 3.2 million (about 9-10% of the population), then similarily
Czechoslovakia with the popultion of about 14 million had roughly about 3.6 million manpower,
with 2.8 million men fit for military service and the mobilization potential of 1.2-1.5 million
(they never fully mobilized though.)
The main problem with Czechoslovakia was that nobody really wanted to defend it (including
"Czechoslovaks" themselves.) There was a huge German minority wanting to reunite
with their Fatherland, Hungarians in southern Slovakia, still remembering Trianon and longing
for Greater Hungary, Slovaks who wanted their own independence and, finally, Subcarpathian
Rus that, culturally, was never a part of Czechoslovakia. Czechs (6.3 million) were a minority
of 47%, and even they were not willing to fight and die for Czechoslovakia.
Such country simply couldn't survive. But still, their army was quite an impressive ground
force (at least on paper, but I wouldn't call them weak in any case.)