Complex sentence: Curtis was having problems because many of his troops were Kansas militia and they refused to enter Missouri, but a force of 2,000 men under the command of Maj. Gen. James G. Blunt did set out for Lexington.
Split into simpler sentences: Curtis was having problems because many of his troops were Kansas militia and they refused to enter Missouri. A force of 2,000 men under the command of Maj. Gen. James G. Blunt did set out for Lexington.