Return of the genius commoner.

If the Synder empire had discovered the plans of the Tigeria empire on time, defending the entire Eastern content would have been 3 times easier. All they would have needed to do was shift most of their forces to the borders, creating an impregnable defence. 

However, now that all of their border cities had been captured, the Tigeria Empire had great access to almost anywhere in the Synder Empire, meaning all sorts of attacks could come anytime from any place. This made allocating Ash corps very difficult, leading to decreased quality of city defence and the loss of cities.

On the other hand, the more cities the Synder Empire lost, the more concentrated their defence would become and the more spread out Tigeria's forces would become. If care wasn't taken, the attacking troops could be wiped out and a counterattack could take place especially since the Synder Empire was yet to show any of their trump cards.