A topic from AEG's L5R CCG Rules forum, copied for Oracle of the Void from a copy of the forum saved in October 2015, so pages it didn't save are missing. Players' names are left out; the rules officials are named. Rulings are as they stood on these dates; later rulings, the rulebooks and the Rules Archive may differ.
A player, 8 September 2008
Ambush Limited: Target one of your unbowed Personalities: Create a battlefield (not at any province). Assign your Personality to attack there. Assign another player’s target Personality to defend there, even if bowed. No other units may move there. Fight a battle there. After it ends, lose 5 Honor.
Shinjo Shono (xp 4) Reaction: Even if Shono is bowed, after Cavalry Maneuvers: Assign one of your target Cavalry Personalities to a battlefield, even if he is bowed. If you are the Defender, straighten him.
The question is; can the Unicorn player use Shono's reaction to assign a second unit (other than the target unit) to the Ambush battle?
Would this carry over to other cards with similar effects?
A player, 9 September 2008
The question is; can the Unicorn player use Shono's reaction to assign a second unit (other than the target unit) to the Ambush battle?
No, because there is no Cavalry Maneuvers before Ambush's battle is fought (see below, emphasis added) therefore Shono's Reaction cannot be taken.
Battles: "Battles created by a card effect that does not create an Attack Phase are treated as normal battles, except: [...] Such battles have no Declaration or Maneuvers segments. Assignment and battlefield creation prior to such battles happen through card effects, and there is no opportunity to invite allies."