Hold Until Spring is the order Major Mark Collins' guerrilla unit received to hold the Japanese advance in the mountains of Idaho and Montana until relieved.
The story is based on the assumption Japan had captured the Hawaiian Islands after Pearl Harbor, then attacked the poorly defended West Coast. Many of the descriptions in this story are true, based on U.S. Army Air Force historical books, U.S. Military Installations in 1939-40, Veterans of Foreign Wars World War II Memorial Edition and the World Book Encyclopedia. Oregon was bombed. The description of the attack at Hamilton and March Fields, the destruction of the air depot at Sacramento, the landing of troops on the California Coast and destruction of aircraft factories, follows a command post exercise drawn up in 1939 by the U.S. Fourth Army to test the West Coast defenses. A military report to Congress, indicating the poor defense conditions of the West Coast, went unheeded because it was believed the Pacific Ocean was the best deterrent.
The movement of Japanese forces and their strategy, after the invasion, is a composite version by present day military historians at Fairchild Air Force Base in Spokane, Washington. The cities mentioned are true except for Peace River, which is a fictional town in the path of the Japanese advance. However, it is based on an actual town with a population of 900, which lies along the river on the highway from Spokane to Clark Fork.