The Red Curtain (or referred by some as the Russian Wall) was a heavily fortified, military wall built by Russia after the Great War that greatly expand across the Russian-European border, which was noted in record to be longer than the Great Wall of China.
In the aftermath of the Great War, Russia was on the brink of numerous unrest and turmoil, and bearing uneasy foreign relations with Western Europe. The unrest reached its peak in August 1921 when French spies were discovered allegedly for encouraging insurrection in which it worsen European-Russian relations. By a month later, in September, the Russian government entered a isolationist period by cutting contact with the outside world and began the construction of the Red Curtain with barbed wires before being finally reinforced with solid concrete by 1926.
In December 1949, the Chimera breached the barrier and invaded Europe. At some point of that year, the United European Defense led an attempted airstrike on the Red Curtain but to only sustain heavy damages from Chimeran anti-aircraft fire. Only eighty percent of downed VTOL crew members were rescued from the failed raid by efforts of their squadron leader, Eric Hudson.
Since the success of Operation Overstrike in mid-1951, human Allied forces have overcome the Chimera in Eastern Europe and were nearing the ruined remains of the Red Curtain in January 1953, with the intention to enter into Russia.