On the Union side, Maj. Gen. Henry W. Halleck, Grant's superior as commander of the Department of the Missouri, was also apprehensive. Halleck had authorized Grant to capture Fort Henry, but now he felt that continuing to Fort Donelson was risky. Despite Grant's success to date, Halleck had little confidence in him, considering Grant to be reckless. Halleck attempted to convince his own rival, Don Carlos Buell, to take command of the campaign to get his additional forces engaged. Despite Johnston's high regard for Buell, the Union general was as passive as Grant was aggressive. Grant never suspected his superiors were considering relieving him, but he was well aware that any delay or reversal might be an opportunity for Halleck to lose his nerve and cancel the operation.