1557
the associated press is reporting that u . s . troops have launched an attack on saddam international airport .
 ( attack: attack,  troops: attacker, saddam international airport: target) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: declare bankruptcy, transfer ownership, transfer money, marry, transport, die, phone write, arrest jail, convict, sentence, sue, end organization, start organization, end position, start position, meet, elect, attack, injure, born, fine, release parole, charge indict, extradite, trial hearing, demonstrate, divorce, nominate, appeal, pardon, execute, acquit, merge organization, Arguments type: beneficiary, prosecutor, plaintiff, seller, victim, buyer, agent, destination, artifact, organization, recipient, person, place, origin, target, giver, adjudicator, attacker, vehicle, defendant, entity, instrument. 
Text: {0} 
Answer:
 ( attack: attack,  troops: attacker, saddam international airport: target) 