Edison Format · March 2010
This effect activates if your opponent's monster is not destroyed during damage calculation.
The attacking monster must be Warrior-Type the entire time from attack declaration until the end of the Damage Step in order to Special Summon "Sword Master".
If your opponent's monster is destroyed by a card effect while your Warrior-Type monster is attacking, it is still not destroyed by battle, so you can Special Summon "Sword Master".
Source: j-wiki Sword Master vs Mystic Swordsman LV2.)