The Battle of Hastings

In 55 b c e, depending on your view of caesar, either because he was just launching a reconnaissance and always planned to come back, or because he underestimated how many people he'd need for the job. Ah, caesar comes back in 54 with a conquest army, five legions, that's 25 thousand men. Thing probably under strength, because let's recall that this is just a little side gig for caesar. At this time, he's in the process of conquering all of gaul and punching the germans in the nose a couple times. I mean, that's the big deal, the main show. This is a side bar gig. He's like that big band