If someone does something that might be illegal, you don't just advance the game state to the first point where it happens to be legal.
The game state is already at the point that the action that the player took is legal. Them doing anything other than completing the sequence of events that they started is what would make the action illegal.
Step one of an attack starts with using the range ruler to measure range and check arcs:
How do we know which ship is the active ship:
"COMBAT PHASE