What is the "cage policy"

The development of anti-Japanese base areas threatens the enemy's rear. From the end of 1938, the Japanese aggressor troops concentrated most of their troops, madly attacked the anti-Japanese base areas behind the enemy lines, and implemented the "cage policy". What is the cage policy? The Japanese army divided and surrounded the anti-Japanese base areas behind enemy lines with traffic lines such as railways and highways, forming a cage and constantly extending to the base areas in an attempt to destroy the base areas in one fell swoop.