Stealing the Enemy’s Urban Advantage: The Battle of Sadr City by John Spencer – Modern War Institute
… Insurgents and guerrilla fighters rely on their ability to move undetected among the population to survive and operate. The Chinese communist revolutionary Mao Zedong counseled fighters to move among the people as a fish swims in the sea. In Baghdad, concrete walls in the sea made it a lot easier to kill or catch fish by creating chokepoints in the terrain that restricted enemy freedom of movement. Using obstacles to restrict insurgent movement in urban military operations is not new. British forces used blockhouses, fences, or other barriers to interdict insurgents in the Second Boer War (1899–1902) and during the 1950s in Malaya. French forces used wire and other obstacles to cordon off entire urban areas in the Casbah during the 1957 Battle of Algiers. Concrete was the barrier of choice in the Iraq War.
https://smallwarsjournal.com/blog/stealing-enemys-urban-advantage-battle-sadr-city
