This is a real thing, it's why units like Sturmtruppen or special forces units have been successful throughout history - a smaller, better trained and coordinated force is often better than a large, uncoordinated mob. _Especially_ if your force is made up of people willing to do suicide attacks. Or if you goal is not to take and hold territory, but to trade lives for terror and body count.

A wave of 1000 soldiers won't break a trench line, but a squad of infiltrators can sneak in and make entry. https://en.wikipedia.org/wiki/Stormtroopers_(Imperial_German...