He was accused of 'assault'. = He was charged with 'assault'. = 'Assault' charges were brought against him.
He came 'under assault' for his unusual beliefs. [=he was severely criticized for his unusual beliefs]
He was found guilty of 'sexual assault'. [=the crime of touching someone in an unwanted sexual way]
(..) We need to control the arsenal inside that fortress. Even with every district in this alliance, I won't commit my people to a ground assault just to pillage weapons. Commander Paylor, your people have suffered Which is why I won't condone a mass suicide. (..)2015 The Hunger Games: Mockingjay - Part 2