Ukraine has destroyed a third bridge in four days, signaling a bold effort to isolate Russian forces and seize additional territory, RadarOnline.com can reveal. Kyiv targeted vital crossings over the River Seym, west of its surprising advance into Russian-held land. The river, about 15 kilometers from the Ukrainian border, runs south of a 550 square kilometer area currently under Russian control. Ukraine hit bridges at Glushkovo and Zvannoe over the weekend, and Russian sources reported a third strike overnight at Karyzh. Professor Michael Clarke told The Sun that these attacks have left Russi…