A First Strike is an interaction in the Paper Mario series in which a battle is initiated with an attack, rather than walking into the other combatant. It can be performed by Mario, his Partners, and even his enemies. When a first strike lands, the battle will start immediately with the attack that caused it, giving that party an advantage by dealing preemptive damage to the opponent(s).
It is almost always best to go for a First Strike whenever possible, unless one wants to prep for a Danger Mario Run and wants to make the process take a little less time. Despite the battle being initiated, a First Strike does not stop the effects of defense or counter-attacks, meaning Mario can guard against it and spiked enemies can still counter.
How to Perform
A First Strike occurs by performing any attack on an opponent without simply walking into them. This includes Jumps and Hammer abilities, as well as partner field moves such as Bombette's explosion. Conversely, enemies can first strike Mario if they have access to any attack such as spinning or firing projectiles outside of battle.
Once in the battle, the First Strike usually does not require any additional Action Commands to function properly.