Sanders is definitely no pacifist. I doubt his foreign policy would differ much from Obama's, he supports Israel and military interventions as much as other Democrats do.
From what I have seen of him, I am pretty sure he'd be much less "hawkish" than Obama. My hope is more attached to that statement. Then again, Obama said the first thing he'd do is close Gitmo. Damn Politicians.
Sanders isn't perfect. He's too pro-Israel. He did vote for the Afghanistan War. But you can trust him more than most politicians, and certainly a lot more than Obama.