Shadow Tactics is a hardcore tactical stealth game set in Japan around the Edo period.
Take control of a team of deadly specialists and sneak in the shadows between dozens of enemies. Choose your approach when infiltrating mighty castles, snowy mountain monasteries or hidden forest camps. Set traps, poison your opponents or completely avoid enemy contact.
Looks to be the same genre as Commandos (if you can remember this far back)
Released: 6 Dec 2016 and £31.49 directly on Steam - Overwhelmingly Positive Reviews
There is also a demo on Steam for those that are undecided