As Hong Kong entered the 16th straight week of unrest, protesters adopted origami cranes as symbols of resistance, sang their new anthem, burned the Chinese national flag, erected barricades, threw petrol bombs and beat opponents unconscious. The protest movement in the semiautonomous region now has taken on characteristics of an insurgency as people across Hong Kong society vigorously challenge local authorities.

The 79-day “Umbrella” protest of 2014, as large as it was, had little lasting effect on Beijing, which has ruled...