>> One of the super secret missions they used to sell the shuttle program was capture
No. That is the easier-to-swallow purpose. The logistics of capturing an enemy sat, one that might defend itself by changing orbit, are ridiculous.
What shuttle could do was bring friendly sats back. Why? Well it would have to be something that you couldn't let burn up in the atmosphere but neverthless needed to come home. Shuttle could have serviced space-based nuclear weaponry, the one type of friendly sat that couldn't be destroyed in the atmosphere or sent into a disposal orbit.
A fleet of nuclear-tipped reentry vehicles in orbit would have required constant up-and-down servicing. Russia saw the US biulding a vehicle capable of servicing such a fleet. Fearing a capability gap, Russia developed Buran. But when various treaties and understandings mooted space-nuke concepts, Buran lost its purpose and was parked. Shuttle continued.
Other aspects of shuttle also came from never-flew military missions. Those giant wings were to permit a polar-orbit overflight of russia with return to the launch center, a cross-range capability. It didn't need such massive wings.