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.
"Suitengu's Torch" reaction reads: After you announce a thunder battle action: It's effects will not be negated or delayed.
At what time does this reaction need to be announced?
a) After the action is declared, but before targeting? b) After targeting, but before resolution?
"Suitengu's Torch" reaction reads: After you announce a thunder battle action: It's effects will not be negated or delayed.
At what time does this reaction need to be announced?
a) After the action is declared, but before targeting? b) After targeting, but before resolution?
The answer is "a)".
Pointedly, the technical term for "declaring" an action as you put it is to "annouce" it (see here), so I'm sure you can see how that makes the timing of Suitengu's Torch's Reaction trigger in relation to taking another action somewhat more clear and exact.