The assembly of the Mark-3 plutonium bomb dropped on Nagasaki was considered dangerous, and orders were given to never assemble a Mark-3 on American soil. In the event of conflict, they would be assembled at intermediate support bases such as Thule, in northwest Greenland. The Mark-3 was complicated and delicate. The trigger was a car battery, which took three days to charge and had to be recharged every week. This required completely disassembling the bomb, which had not been designed for this, and therefore required considerable time. By 1947, the United States had enough plutonium to assemble several dozen Mark-3s, but only one was operational and several were partially built.
