Short answers, pulled from the story.
Counterinsurgency is the totality of actions aimed at defeating irregular forces. The Oxford English Dictionary defines it as any military or political action taken against the activities of guerrillas or revolutionaries, and it can be considered war by a state against a non-state adversary.
David Galula proposed that the aim of war is to gain the support of the population rather than control of territory, that most of the population stays neutral and can be won with an active friendly minority, that the population must be efficiently protected so it can cooperate without fear of retribution, and that order should be enforced progressively, area by area, using pacified territory as a base. He summed up counterinsurgency as building or rebuilding a political machine from the population upward.
Dr. Lorenzo Zambernardi argued in Counterinsurgency's Impossible Trilemma that a counterinsurgent cannot simultaneously achieve force protection, distinction between combatants and non-combatants, and the physical elimination of insurgents. A state must choose two of the three goals and sacrifice the third.
Drain the sea, also called drain the water, is the forced relocation or elimination of the civilian population to expose the insurgents hidden within it, depriving them of support, cover, and resources. Examples include the Bar Kokhba revolt, the Second Anglo-Boer War, the Greek Civil War, the Rohingya conflict, and the Xinjiang conflict.
Martin van Creveld argues that almost all attempts to deal with insurgency have ended in failure and that the core difficulty is moral rather than military or political. He compares the strong counterinsurgent to an adult fighting a child, who feels unjust if he harms the child and foolish if he is harmed, and he advises throwing overboard 99 percent of the existing literature because most was written by the losing side.
The Briggs Plan, implemented fully in 1950, relocated Chinese Malayans into protected New Villages designated by British forces. By the end of 1951, some 400,000 ethnic Chinese had moved into the fortifications, and the British formed a Home Guard among them against the Malayan Communist Party.