Complex sentence: Washington had sent General Varnum to Fort Mifflin in November to quell the frequent command disputes between garrison and naval commanders with little success, faulted himself and offered his apologies to Washington.
Split into simpler sentences: Washington had sent General Varnum to Fort Mifflin in November to quell the frequent command disputes between garrison and naval commanders with little success. Varnum faulted himself and offered his apologies to Washington.