# Who has stirred up one from the east, calling him in righteousness to his service?

"I am the one who called this powerful ruler from the east and put him in my good service." 

# He hands nations over to him

"I give the nations over to him" or "The one who does these things hands nations over to him"

# subdue kings

"conquer kings and force them to obey him"

# He turns them to dust with his sword, like windblown stubble with his bow

The armies of one from the east will conquer these nations and scatter the people easily.