Just started playing and had a few questions on this scenario.
1. Can the us arty fire even if nva have not entered their patrol radius?
2. I assume that each hexes patrol radius governs the activation of its own hex, ie nva troops need to enter its radius not just any hexes radius?
1. It only says US units may not move, so the Artillery can fire.
2. From the scenario card "US units may not move unless a PAVN unit enters the patrol radius of any Patrol marker via movement, retreat, or combat refusal."
So if a PAVN unit enters any of the patrol radius, then all of the US units may move.