Having a railroad functional enough for military purposes is easy enough: get the rails hooked up. Put soldiers at switches to flip them, use radio for coordina

Having a railroad functional enough for military purposes is easy enough: get the rails hooked up. Put soldiers at switches to flip them, use radio for coordination. For high speed high frequency passenger travel it's more complicated: you need automation flipping switches at the right times, automatic block signaling to ensure that trains are where they're supposed to be and won't crash into each other, etc. That's why they were able to get some of the trains back to operation: they can't run them as close together as before, but can still use the tracks.