The very act of preventive attacks is extremely advantageous, as it catches the enemy days or weeks behind, and allows you to perform much better initially, which translates to later advantages as well. The reason Hitler could advance so much against the Soviets is due to that. The reason he conquered France was also due to that. Note that it was called "Blitzkrieg" because it was fast - but actually Germans were just really good. It wasn't an actual tactic, it's just what happens if your soldiers aren't busy fucking every civilian on the way.