Situation came up last night that neither my opponent or I were sure of the right answer to. Model A is inside a Nimbus grenade field, and declared their first short as a move, and moved to the edge of the cloud but still out of LoF to Model B who was an inch or two outside the smoke. Model As intention was then to use their second short to move up, get into base to base with Model B, thus engaging the model outside the smoke. Usually (without the smoke) this is straightforward. Model B could declare an ARO after the first short and shoot as they have LoF etc. With smoke in play we initially thought you could just delay their ARO to shoot during the second short (since they can't see Model A at the end of the first short, and then could during the second) However given the close quarters at play here, Model As first move order was within Model Bs ZoC, thus there *were* legal AROs that Model B could declare after that first short. (alert etc) So our question was whether Model B could still delay their ARO and then shoot when Model A appeared from smoke, or were they now forced to declare an available ARO after the first short since it was within their ZoC and they had valid AROs available (and thus do not get the opportunity to shoot as Model A was still outside of LoF when the first short ended)
Assuming you meant smoke rather than Nimbus (Nimbus Zones don't block LoF), the reactive trooper would have a choice of declaring Change Facing or some other ARO that doesn't require LoF, or not declare an ARO at all. You only get to delay an ARO if the active trooper is in a marker state such as Camouflaged, or the reactive trooper has Sixth Sense and the active trooper is within Zone of Control. Otherwise, AROs are strictly use it or lose it. See http://infinitythewiki.com/en/ARO:_Automatic_Reaction_Order in particular: 'The Reactive Player must declare AROs for all eligible troopers immediately after the Active Player declares his Entire Order or the first Short Skill of his Order (see: Order Expenditure Sequence). Troopers that fail to do so lose their ARO against that Order.'
Model B has a valid ARO at the end of the first short skill. If model A moves without stealth in ZoC of model B and without LoF, model B HAS to declare an ARO at that time or forfeit it all together. The only way model B could hold his ARO is if model A is in a marker state or Model B has sixth sense. This is an intentional part of the ruleset to make getting into CC easier.
Unless Model A had Stealth? Stealth is usually played as automatically on, which means that when Model A moves within ZoC (but outside LOF) of Model B it doesn't trigger an ARO unless you turn Stealth off (by saying 'I Move without Stealth'), and then they do.
