War on the Rocks has an interesting piece on the apparent development of a Bastions as both defensive and offensive positions.
Bastions are not a new development. World War II offers many examples of both success and failure. Singapore was a British bastion in WWII lost to the Japanese. One could say that Pearl Harbor was a bastion attacked December 7,1941. Malta was a bastion that was besieged for 29 months, from which the British attacked Axis supply lines to North Africa by submarine, surface ship, and aircraft.
The Japanese had Rebaul and Truk as well as many additional fortified island bases. As they pushed further from the homeland, the protected perimeter increased and consequently defenses became thinner and more porous. The US bypassed many of these, leaving them to “wither on the vine.” The months long battle between what became the US bastion at Guadalcanal and Tulagi in the Southern Solomon Islands and the Japanese at Rebaul, New Britain was a good example of a battle between Bastions.
What has changed is the range of influence these bastions now have. Bastions in the South China Sea can now reach Guam with both ballistic missiles and air launched cruise missile.
The Coast Guard is already at two of locations sighted as existing or possible future bastions, Guam and Bahrain.