Complex sentence: Perhaps the most compelling explanation relates to Cannon's experience serving as a detachment leader under General Jackson's command during the Creek War, when he believed that Jackson treated his men unfairly and exposed them to unnecessary risk.
Split into simpler sentences: Perhaps the most compelling explanation is that Cannon disapproved of General Jackson's military leadership when he was a detachment leader under Jackson's command during the Creek War. Cannon believed that Jackson treated his men unfairly and exposed them to unnecessary risk.