Dead Fall by Brad Thor

 Scot Horvath is facing one of his most daunting challenges yet. He has to head into war-torn Ukraine to retrieve an American woman named Anna who was kidnapped by Russian mercenaries while trying to protect an orphanage. To make things even more challenging, he has to do it without his usual well-trained team, instead relying on a handful of volunteers he meets for the first time in Ukraine. And his opponents are ruthless. It makes for a timely and compelling story.