That's the third time in the first season of that there is a bunch of mercenaries trying to take over south of California and the south border. The other ones were The Night of the Red-Eyed Madmen (1965) and The Night of the Fatal Trap (1965).
The mercenaries are planning to attack Baja California, which is a peninsula in Mexico south of the US state of California, comprising roughly 56,000 square miles. In the 1870s it was a sparsely populated territory of Mexico with a population around 40,000.
Ross Martin and Keenan Wynn previously appeared together in The Great Race (1965)
First episode in the series in which West neither kisses a woman nor is seen shirtless (two standard tropes for the show's hero).
Theatrical debut of James Gammon, who was also known for notable roles in Major League (1989) and Silverado (1985).