Here's a take on the reasons behind the erection of the Berlin Wall, a Cold War symbol:
"during the 1950s, American cold warriors in West Germany instituted a crude campaign of sabotage and subversion against East Germany designed to throw that country’s economic and administrative machinery out of gear. [...]
The United States and its agents used explosives, arson, short circuiting, and other methods to damage power stations, shipyards, canals, docks, public buildings, gas stations, public transportation, bridges, etc; they derailed freight trains, seriously injuring workers; burned 12 cars of a freight train and destroyed air pressure hoses of others; used acids to damage vital factory machinery; put sand in the turbine of a factory, bringing it to a standstill; set fire to a tile-producing factory; promoted work slow-downs in factories; killed 7,000 cows of a co-operative dairy through poisoning; added soap to powdered milk destined for East German schools; were in possession, when arrested, of a large quantity of the poison cantharidin with which it was planned to produce poisoned cigarettes to kill leading East Germans; set off stink bombs to disrupt political meetings; attempted to disrupt the World Youth Festival in East Berlin by sending out forged invitations, false promises of free bed and board, false notices of cancellations, etc.; carried out attacks on participants with explosives, firebombs, and tire-puncturing equipment; forged and distributed large quantities of food ration cards to cause confusion, shortages and resentment; sent out forged tax notices and other government directives and documents to foster disorganization and inefficiency within industry and unions"...
Source and more: Consortiumnews.com, July 28, 2011