Why doesn't my trigger put data into my table?
What learning_DBAdmin is saying makes sense... 
if this is the only script you are running, it will only create the trigger... 
when you insert or update the table tAttackPlan, it will trigger the trAttack trigger. 

Now let's analyze the trigger... If an insert or update is done on the tAttackPlan table the trigger will insert into tAttackPlan the attack date and domainID... Is this what you really want? It seems to be recursive to me but not sure of the whole story behind this piece of code. ... What I see is if your trigger is triggered it will insert into the tAttackPlan table which will trigger the trAttack again, and so on and so forth. 

Also, note that a trigger has 2 internal tables inserted and deleted, which define the new value of the insert/update (in inserted) and the old value or records to delete (in deleted)... 

Please check Microsoft sites to see how triggers work.