Trojani Graecis fortiter resistunt

[itaque]

I'm working through a Latin textbook, and I'm trying to translate "Trojani Graecis fortiter resistunt."

I'm guessing this is best translated "The Trojans bravely resist the Greeks," but why is "Graecis" in the dative case? Shouldn't it be accusative? (i.e., Graecos)

 

[Pacifica]

While the English verb "resist" takes a direct object, the Latin resisto doesn't but takes the dative instead.