However, a full-spectrum analysis of the Nigeria case suggests that this popular dominant narrative scarcely scratches the surface of the true COIN challenge. This population-centered challenge, moreover, is one that militaries across the world continue to contend with. And in attempting to solve the COIN puzzle, state forces over the decades have tried a range of tactics. Information-centric theory Starting in the early 2000s, micro-level data has transformed the analysis of effective counterinsurgency (COIN) operations. Leading this work is the "information-centric" group of theorists and researchers, led by the work of the Empirical Studies of Conflict (ESOC) group at Princeton University, and the Conflict and Peace, Research and Development (CPRD) group at the University of Michigan. Berman, Shapiro, and Felter have outlined the modern information-centric model. In this framework, the critical determinant of counterinsurgent success is information about insurgents provided to counterinsurgents, such as insurgent locations, plans, and targets. Information can be acquired from civilian sources (human intelligence, HUMINT), or through signals intelligence (SIGINT). Tactics "Drain the sea" tactic With regard to tactics, the terms "drain the sea" or "drain the water" involves the forced relocation or elimination of the civilian population ("water") to expose the rebels or insurgents ("fish"). In other words, relocation deprives the aforementioned of the support, cover, and resources of the local population. This is typically targeted in that it specifically targets the demographic that supports the insurgency in a limited area where insurgency is taking place, but is indiscriminate from an individual perspective. Examples of use of this technique in counterinsurgency include Bar Kokhba revolt, Second Anglo-Boer War, Greek Civil War, General Order No. 11 (1863) in the American Civil War, Rohingya conflict, and Xinjiang conflict. "Draining the sea" can also be accomplished through genocide by killing the population blamed for the insurgency. During World War II, Nazi Germany's counterinsurgency (, ) became intertwined with the Final Solution. Indiscriminate violence also has a deterrent effect. Edward Luttwak stated, "A massacre once in a while remained an effective warning for decades." A downside of such methods of counterinsurgency is their severity may provoke increased resistance from the targeted population. In contemporary times, concerns about public opinion and international law can rule out counterinsurgency campaigns using indiscriminate violence. Assassination of leaders Assassination of leaders can be a successful counterinsurgency tactic. Oil spot The oil spot approach is the concentration of counterinsurgent forces into an expanding, secured zone.