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, 2 September 2007
Note that while you are still in the Action Phase, you are also in the Combat Segment or Resolution Segment of a Battle for most of it. The rules governing those segments (including whether or not you can take certain actions during them) still apply. You need Battle Actions, not Open or Limited Actions, during a Combat Segment.
Marty Lund - Deputy Rules Monkey
(Comprehensive Rules: Glossary A, Additional) 1. Some effects grant an “additional” phase or segment within the sequence of play.
The additional phase or segment occurs immediately, regardless of what phase of segment the sequence of play is currently in.
During the additional phase or segment, the game is considered to be in that phase or segment, rather than in the phase or segment during which the effect occurred. For example, if a Limited action creates an attack during the Action Phase, the game is considered to be in the Attack Phase and not the Action Phase for the duration of the attack.
After the additional phase or segment finishes, the phase or segment in which it was created resumes.
Because Ambush does not grant or create a Combat Segment or Resolution Segment, (just the Battlefield & ensuing Battle, which happens to involve both Segments) does it still follow the rules quoted for shifting between Action & Attack phase during those Segments?
Martin Lund (rules official), 4 September 2007
Note that while you are still in the Action Phase, you are also in the Combat Segment or Resolution Segment of a Battle for most of it. The rules governing those segments (including whether or not you can take certain actions during them) still apply. You need Battle Actions, not Open or Limited Actions, during a Combat Segment.
Marty Lund - Deputy Rules Monkey
(Comprehensive Rules: Glossary A, Additional) 1. Some effects grant an “additional” phase or segment within the sequence of play.
The additional phase or segment occurs immediately, regardless of what phase of segment the sequence of play is currently in.
During the additional phase or segment, the game is considered to be in that phase or segment, rather than in the phase or segment during which the effect occurred. For example, if a Limited action creates an attack during the Action Phase, the game is considered to be in the Attack Phase and not the Action Phase for the duration of the attack.
After the additional phase or segment finishes, the phase or segment in which it was created resumes.
Because Ambush does not grant or create a Combat Segment or Resolution Segment, (just the Battlefield & ensuing Battle, which happens to involve both Segments) does it still follow the rules quoted for shifting between Action & Attack phase during those Segments?
"Fight a battle there," indicates that you must proceed through a Combat Segment and Resolution Segment for that Battle at the Battlefield created.
This does not create an Attack Phase, so it does not suspend the Action Phase. There was no Segment at the time of the Ambush, so no Segment is suspended. During the Combat Segment and Resolution Segment you must abide by the Segment's rules about what actions you can take - if any.
In short: No Attack Phase No Limited or Open Actions It is still the Action Phase You still abide the rules for the Combat and Resolution Segments