Many clear days for year-round flying,central position for easy access and a temperate climate.
Explanation:
With clear days for year round flying, it was easy to train the military and also keep a watch on enemies. Okhlama's central position for easy access made it possible for several army men to join the training sessions and also allowed easy transport to and fro defense factories.
In addition, a temperate climate made military training easy and not very challenging for the military personnel. A very hot or cold climate would have not made training possible for several hours together.
