[masswerk]

Regarding Buran: Delivery of nuclear weapons was part of the specs of 1950s XB-20 Dyna-Soar project (https://en.wikipedia.org/wiki/Boeing_X-20_Dyna-Soar). The soviets probably saw the obvious similarities in the basic design, probably also knew about the Space Shuttle specs having been blown up in an otherwise inconceivable fashion by request of the armed forces and drew their conclusions, eventually answering the threat by coming up with a design that actually adhered to these assumed specs. It was a necessity dictated by panic.