Steve McQueen and James Coburn also appear together in The Magnificent Seven (1960) premiering the same year. They would also co-star later in The Great Escape (1963).
The battle in question took place on October 14, 1863, and it is said the events here were 6 years later, making the year of the events circa 1869. As an overall timeline for the series, this is more or less consistent with Season 2's Black Belt (1960) where the events took place circa February 1867.