The film had real potential, but it’s ultimately undermined by some unfortunate casting choices. I honestly believe I could have delivered a more convincing performance as “Bleeker” than Fess Parker, whose acting feels stiff and unnatural. It's often possible to imagine director Melvin Frank prompting him—perhaps even just urging him to breathe—due to his halting delivery which drains much of the vitality from the story. Jeff Chandler isn’t exactly setting an example either in his role as a man attempting to establish an independent republic in Kansas. "Darcy," the military governor, played by Herbert Rudley, learns about this plan and sends “Meeker” to expose the would-be president to the cavalry. This turns out to be fairly straightforward since the leader’s strategy involves using his armed “Jayhawkers” to convince people that he offers the best, or only, option available. "Bleeker" is also motivated by a personal vendetta, blaming this man for his wife's death, so the central question becomes: will he manage to set a final trap for "Darcy," or will that clever individual recognize the deception and fight back? There’s considerable action throughout, and it functions reasonably well as an early look at the period leading up to the Civil War, when the United States was essentially a collection of rival communities governed by strong, charismatic, and militaristic leaders. The only real threat comes from Henry Silva's portrayal of "Lordan," but generally this is a rather disappointing western that suffers from weak writing and a Chandler who evokes “Captain Nemo” more than a brutal leader.

Source on TMDB