Which preposition to use with helvetii

in Occurrences 3%

He, therefore, undertakes the affair, and prevails upon the Sequani to allow the Helvetii to march through their territories, and arranges that they should give hostages to each otherthe Sequani not to obstruct the Helvetii in their marchthe Helvetii, to pass without mischief and outrage.

Which preposition to use with  helvetii