There are few today who have their level of physical conditioning and military training.
History has numerous examples of small bodies of highly trained men holding at bay vastly superior enemy forces.
At the Battle of Maldon in 991 A.D. three warriors, Wulfstan, Aefhere, and Maccus, successfully held a narrow coastal causeway against a Viking army of nearly 4000 men. They only retreated when ordered to do so by their lord, the Ealdorman Brythnoth.