Liberty Defense Perimeter

The Liberty Defense Perimeter is a boundary line that serves as the main part of the United States Department of War's plan for defending America against the Chimera. In the event of an alien invasion, the area within the LDP will serve as a sanctuary for humanity while the perimeter itself will be fortified with Liberty Defense Towers. Final fortification of the line is scheduled to be completed in July 1952.

History
The idea was first mentioned in an analysis of enemy battle tactics. Discussing hypothetical invasion scenarios, the document notes that while an attack from the coasts or from Alaska would overwhelm any resistance, an attack from the northeast would allow for the creation of a heavily armed "Liberty Zone" in the southern United States and lead to a stalemate. It appears that the government used the Liberty Zone concept as inspiration for the LDP project.

=Evacuation Plan=

Once the mathematically inevitable invasion of America begins, the government will be moved inside the LDP, followed shortly thereafter by essential personnel, House and Senate members, and priority personnel, as well as any immediate family members they may have. They will be followed by military forces assigned to guard the zone. Once they have arrived, civil authority will allow for some groups of civilians to enter the area.

=Defense=

A War Department memo describes the Liberty Defense Tower program, which consists of a series of 1,400 foot tall towers placed every 50 feet along the LDP. The towers are armed with concussion shells that can fire at targets up to 30 miles away. President Grace has approved construction of the buildings, and they are scheduled to be completed in September 1951.