Royal Tan and FSNA (Federation of states national army) Troops dig in along the border, this area is important because it's the area where the 3 countries join. If the Imperial Greens wanted to they could spearhead along the Federation and Tans border to cut them off from each other. Seeing this as a huge threat the Tans and Federation create a coalition against the Greens and begin to fortify their strategic locations, and also create divisions with soldiers from both countries.