Iraqi troops and their allies are getting closer and closer to Mosul. Forces at the head of the advance, approaching the city from the east, have even crossed into the city's outskirts. Islamic State fighters in the heart of Mosul have begun to prepare for the impending battle, and based on satellite imagery obtained from our partners at AllSource Analysis, it appears as if the jihadist group has formed a formidable defensive line along the southern edge of the city's center. The photographs above, taken Oct. 31, show that the Islamic State has cleared a wide swath of terrain to the north of Mosul airport, along the western bank of the Tigris River. Nearly all of the buildings in the airport complex and the former military base to its west have been leveled.