During the seventh mission of the campaign where you had to defend the base in the crater, and then destroy a superturrent and a Covenant encampment you had the control over eight SPARTAN-IIs: Douglas, Alice, Jerome and the five nameless Spartan-IIs whom simply read: OMEGA TEAM.
Actually there were only 25 SPARTAN-IIs with the status of green during the campaign of Halo Wars, so where you got the number of 50 beats me. You most likely have read that piece of toiletpaper written by Alex Garland and passed of as a script. His script *** starts with 50 SPARTAN-IIs clad in MJOLNIR armor fighting a bunch of Sangheili.