REDU format ruling
Swift Samurai Storm!

Nearest-era rulings (Tengu, Sept 2011) — no REDU-specific archive exists.
Card effect (current official text)Each turn, after the first time a "Six Samurai" monster you control battles, all "Six Samurai" monsters you control gain 300 ATK until the end of this turn.
Rulings
- You cannot activate this card during the Damage Step.
- This card’s ATK increasing effect does not start a Chain.
- The ATK increase happens at the end of the Damage Step the first time a "Six Samurai" monster you control battles that turn.
- Any given "Six Samurai" can only gain the ATK increase once per turn, after the first time a "Six Samurai" battles while it is on the field. (Example: You control 2 "Six Samurai" monsters, Irou and Yaichi and a face-up "Swift Samurai Storm!". Irou battles, and Irou and Yaichi gain 300 ATK. If you then use "Call of the Haunted" to Special Summon "The Six Samurai – Nisashi", he will not automatically gain 300 ATK. If Yaichi battles, then Nisashi will gain 300 ATK.)
- If "The Six Samurai – Irou" attacks a face-down monster and destroys it with his effect, it is not considered to have been destroyed by battle. The effect of "Swift Samurai Storm!" will not be applied.
- The ATK increase only affects "Six Samurai" monsters that were face-up when it was applied.
Rulings data courtesy of Format Library — formatlibrary.com. Spotted an inaccuracy? Flag it in the REDU forum — sourced change requests get reviewed.