I am trying to add an additional invasion tactic. I added this to the invtactics

    <InvTactic InternalName="RoboSoldiers">
        <DisplayName>Robotic Soldiers</DisplayName>
        <Description>Robotic Soldiers</Description>
        <Tech_Requirement>MechanizedWarriors</Tech_Requirement>
        <Image>Tactics_Bots</Image>
        <Cost>500</Cost>
        <LuckFactor>60</LuckFactor>
        <PreRequirement>0</PreRequirement>
        <PreReqValue>0</PreReqValue>
        <BonusType>1</BonusType>
        <BonusValueMin>100</BonusValueMin>
        <BonusValueMax>150</BonusValueMax>
        <PlanetQualityPenaltyMin>0</PlanetQualityPenaltyMin>
        <PlanetQualityPenaltyMax>0</PlanetQualityPenaltyMax>
        <InfluencePenaltyMin>0</InfluencePenaltyMin>
        <InfluencePenaltyMax>0</InfluencePenaltyMax>
        <ImprovementPenaltyMin>5</ImprovementPenaltyMin>
        <ImprovementPenaltyMax>10</ImprovementPenaltyMax>
    </InvTactic>

However, when I research mechanized soldiers, this additional invasion tactic does not show up. What have I done wrong?