A great idea not taken to it's full potential
Plot wise the game is fairly straight forward, you take on the role of a member of the doomed 7th Calvary Column commanded by George Custer at the Battle of the Little Bighorn, who is saved from the fate his comrades met by a time traveler who takes him 300 years into the future, where the former Calvary soldier is made into a time cop, and tasked with tracking down a missing scientist.
Over the course of the game you get to experience many familiar time periods including World War I, the American Civil War, the Indian Wars, and World War II. Each time period is well researched, and presents the player with a wide variety of weapons unique to the specific time period, which can be upgraded once the player returns to future, and the Civil War Era weapons are given quicker reload times.
However the problems begin with the idea that some enemies have to be kept alive, and this is made all the more difficult by being provided with a limited number of stun grenades which can't be replenished, this makes completing a mission without killing someone who has to be kept alive all but impossible. The other problems this game has lie in it's poor hit detection and brain dead AI.
At times the hit detection is so poor that you wonder how you missed, example during a mission set during World War I, you have numerous chances to shoot an advancing German Infantry officer in the face with a rifle, yet the game won't register the hit, while most weapons like Civil War era guns weren't known for their accuracy, the game designers could have at least made sure hitting the enemy wasn't simply good luck.
While the Hit Detection is in need of a major over hall, the brain dead AI all but negates the need for an over hall, since many enemies will simply run into rocks or trees and stay there shooting blindly at you as you pick them off one by one.
While Darkest of Days isn't the worst game, earning a lot of points for being original, and introducing wars that have rarely been featured in video games, it's a game that feels incomplete and boils down to just another FPS. Had the developers taken time to fine tune the story, improve the hit detection and AI, then this game would have been a must have, instead we get a game that will mostly appeal to history buffs and casual FPS fans