Is this sentence correct (grammarwise)?

1. 
   
   If the Wall was attacked(attack) by enemies, the soldiers at the turrets would run (run) to the nearest milecastle for help or would light(light) a fire that could be seen(can / see) by the soldiers in the milecastle. a
   

My particular doubt is for the first verb: If the Wall was attacked/ were attacked/ had been attacked/ would have been attacked.

Thank you,

Brazilian Pedagogical Grammar student in Jerusalem.