Frederick the Great famously noted after the Battle of Zorndorf that "It's easier to kill the Russians than to win over them."
For that same battle the Russian commander (William Fermor) is noted as having drawn up his forces in front of a swamp, allegedly to deter his young conscripts from retreating away from Frederick's famous oblique attack.
Other contemporary sources note the frequency with which Russian infantry was drawn up with Cossacks so close behind that "the breath of the horses warmed the hair on the back of their necks".
Is there any consensus on the relative extent to which cultural, tactical, psychological and other factors contributed to the observed willingness of Russian soldiers to stand and die in exceptional numbers? The time period of interest would run from 1756 to 1815.