Soldier can be used for Protection. Soldier is related to Fighter. 
Alarm can be used for Warn. Warn is a type of Order. Order is related to Last. Last is the opposite of Front. 
Protection <--UsedFor-- Soldier <--RelatedTo--> Fighter 
Alarm --UsedFor--> Warn --IsA--> Order <--RelatedTo--> Last <--Antonym--> Front 