The Finnish troops at Tali-Ihantala summer 1944. The massive operation by the Red Army was stopped in its tracks. They need not be special troops, they just believed they could win. They stopped the Red Army. The fact we are independent proves it.
why did the navy stop getting pickles in glass jars? Navy corpsmen got tired of getting marines heads out of the jar. that said, USMC and Royal Marines probably best "large"(able to deploy in battalions or larger) units. Issue in WW2 with any unit was replacements not being as well trained as original unit. many US infantry divisions suffered over 100% casualties. On SEALs: still haven't figured out how a unit started to do underwater obstacle removal and beach recon turned into a unit doing parachute operations 400+ miles from nearest water.