The Fall of Ostri was a major event in the early stages of the Locust War that would shape how the war would be fought.
Since E-Day, Premier Deschenko was fighting for control of Ostri against the Locust Horde. Losing over twenty brigades of Gears, he was unable to defend both the northern border of Pelles and Ostri. Unable to gain help from any other COG nations or the Chairman himself, Deschenko ordered a retreat from the whole country.
With the fall of Ostri and it's proximity to Pelles, Deschenko had a refugee problem and was unable to defend his northern border, but was reminded to use chemical weapons for his endgame. However, for the newly seated Chairman Richard Prescott, Ostri falling made the remaining COG nations more desperate and forced them to think within their own borders. Prescott was unable to gain the help of any other member states (Except for the South Islands) for a counterattack against the Locust heart of infestation (Which ironically was in Tyrus). Prescott decided that only the Hammer of Dawn was able to win the war since the Locust are within weeks of marching into Ephyra.