Regions are adjacent if they share a common border. To break it down in more detail, here is a list of each region, and the regions that are considered adjacent to it:
Deployment zones: Regions 1-6
Region 1: Deployment zones and region 5
Region 2: Deployment zones and region 6
Region 3: Deployment zones and region 6
Region 4: Deployment zones and region 5
Region 5: Deployment zones and regions 1, 4, 6, and 7
Region 6: Deployment zones and regions 2, 3, 5, and 7
Region 7: Regions 5, 6, and 8
Region 8: Region 7