On December 7th, 1952, Axbridge was hit by a surprised attack by the Chimera. The attack was believed to be a strategic attempt to divert British military forces from making further advances in mainland Europe. Colonel Rachel Parker requested SRPA's assistance in the form of Specter Team, culminating in Operation Allied Shield.
By December 12th, Specter was successful in repelling the Chimera, in which the Chimera's strategy had turned against them as European forces were able to attack the European continental Chimeran towers, which are poorly defended. As a result of Allied Shield, British Intelligence provided America with detailed schematics of nuclear reactor configuration that were reversed engineered from Chimeran reactor core, and allowing SRPA NT to develop an advanced fission bomb.