What is "Preemptive Strike Increase" and how does it interact with "Preemptive Strike Debuff"?

In your Research Academy, the 'Preemptive Strike Increase" research firstly enables your Troops to participate as attackers in the Preemptive Strike phase of a battle (if you don't have any points in this research, your Troops can only defend during the Preemptive Strike), and then also increase your attack during the Preemptive Strike phase.

Unique among other buffs, the Preemptive Strike attack buff increase is applied after all of your other buffs are applied. This means that if you are at precisely 1000 BASIC Troop Attack, after all of your buffs are applied and your Preemptive Strike Increase is 100%, then you have 2000 Attack during Preemptive Strike.

Based on that, the Preemptive Strike debuff applies to the Preemptive Strike buff like other debuffs. So if your opponent has 50% debuff and you have 100% buff, then your Preemptive Strike Attack is 50% in total which means that your theoretical 1000 Troop attack will be increased to 1500 instead of 2000.

Remember that if you ever decide to analyze your battle report, Preemptive Strike buffs and debuffs DO NOT apply in the main battle phase.