message: Howitzer requires Flight, Mobile Artillery requires Computers
diff: <bUnitAI>1</bUnitAI>
  </UnitAI>
  </UnitAIs>
  - <PrereqTech>TECH_ASSEMBLY_LINE</PrereqTech>
  - <TechTypes>
  - <PrereqTech>TECH_BALLISTICS</PrereqTech>
  - </TechTypes>
  + <PrereqTech>TECH_FLIGHT</PrereqTech>
  <BonusType>BONUS_IRON</BonusType>
  <iCost>200</iCost>
  <iAdvancedStartCost>100</iAdvancedStartCost>
  <bUnitAI>1</bUnitAI>
  </UnitAI>
  </UnitAIs>
  - <PrereqTech>TECH_ROCKETRY</PrereqTech>
  + <PrereqTech>TECH_COMPUTERS</PrereqTech>
  <BonusType>BONUS_OIL</BonusType>
  <PrereqBonuses>
  <BonusType>BONUS_IRON</BonusType>
  