Attack on titan is a manga series written and illustrated by janpaness.
I wonder why the title is 'attack on titan' not 'attack titan'.
cf. The man attacked him with a knife.
I think attack is 'transitive verb' so, 'on' is not necessary. Why does the title need 'on'?
Is there any difference(or nuance) between 'attack on titan' and 'attack titan'?