The developers recently confirmed that only turn numbers contribute towards an S-Ranking. So, throw caution to the wind and focus on speed over limiting casualties for the S-Ranks. Netting an S or A-Rank will also get you 3 stars on that map.I'm S-Ranking each mission as I play through the campaign before moving on. I may not be the fastest, but I wanted to post them as I did them incase anyone wanted something to aim for. If someone reports a higher turn count still qualifying for an S-Rank I'll edit it in parenthesis after my time.Also, here is a wonderful playlist on YouTube courtesy of Tully123 showing his S-Rank playthroughs. They should help to give you an idea of what to expect and potential methods to use if you're struggling! The video doesn't embed into the solution since it's an entire playlist, so here are some emoticons for visibility!Prologue: 8 turnsAct 1 Mission 1: 3 turnsAct 1 Mission 2: 11 turns (Thanks Squ4rex Act 1 Mission 3: 7 turns (Thanks Squ4rex Act 1 Mission 4: 11 turnsAct 2 Mission 1: 14 turnsAct 2 Mission 2: 13 turns (14 turns also reported)Act 2 Side Mission 1: 16 turnsAct 2 Side Mission 2: 13 turnsAct 2 Side Mission 3: 5 turnsAct 3 Mission 1: 7 turns (13 turns also reported)Act 3 Mission 2: 20 turns (21 turns also reported)Act 3 Mission 3: 16 turns (17 turns also reported)Act 3 Side Mission 1: 23 turnsAct 3 Side Mission 2: 19 turnsAct 4 Mission 1: 15 turnsAct 4 Mission 2: 8 turns (14 turns also reported)Act 4 Mission 3: 14 turnsAct 4 Side Mission 1: 9 turns (12 turns also reported)Act 4 Side Mission 2: 6 turns (7 turns also reported)Act 5 Mission 1: 12 turns (13 turns also reported)Act 5 Mission 2: 15 turns (17 turns also reported)Act 5 Side Mission 1: 25 turns (26 turns also reported)Act 5 Side Mission 2: 20 turnsAct 5 Side Mission 3: 17 turns (19 turns also reported)Act 6 Mission 1: 11 turns (12 turns also reported)Act 6 Mission 2: 15 turns (17 turns also reported)Act 6 Mission 3: 17 turnsAct 6 Side Mission 1: 20 turns (21 turns also reported)Act 6 Side Mission 2: 20 turnsAct 7 Mission 1: 13 turns (14 turns also reported)Act 7 Mission 2: 18 turns (19 turns also reported)Epilogue: 37 turns (40 turns also reported)If anyone wants to contribute their numbers let me know! Especially if you S-Ranked a stage I haven't done, or with a higher number of turns than I!Most of the campaign missions I managed to get first try, but the side missions seemed much more difficult to hit good times on. Act 7 Mission 2 was particularly brutal, though, and took me about 5 victories until I was quick enough.If anyone has questions about a particular mission strategy ask in the comments and I can try to help.