A small nation - what could they add? Well, you have to understand the character of the people of Finland. Here's a datapoint.
During the Winter War (1939–1940) between Finland and the Soviet Union, Häyhä served as a sniper for the Finnish Army against the Red Army in the 6th Company of JR 34 during the Battle of Kollaa in temperatures between −40 °C (−40 °F) and −20 °C (−4 °F), dressed completely in white camouflage. Stalin’s purges of military experts caused chaos, and Soviet troops were not issued with white camouflage suits for most of the war, making them easily visible to snipers. Häyhä has been credited with 505 sniper kills. A daily account of the kills at Kollaa was made for the Finnish snipers. All of Häyhä's kills were accomplished in fewer than 100 days – an average of just over five kills per day – at a time of year with very few daylight hours.Hat tip Claude.
Häyhä used an M/28-30, with serial number 60974, because it suited his small frame (1.6 m (5 ft 3 in)). The rifle is a shorter, Finnish White Guard militia variant of the Mosin–Nagant rifle, known as "Pystykorva" (literally "Spitz", due to the front sight's resemblance to the head of a spitz-type dog) chambered in the Finnish Mosin–Nagant cartridge 7.62×53R. He preferred iron sights over telescopic sights as to present a smaller target for the enemy (a sniper must raise his head higher when using a telescopic sight), to increase accuracy (a telescopic sight's glass can fog up easily in cold weather), and to aid in concealment (sunlight glare in telescopic sight lenses can reveal a sniper's position). As well as these tactics, he frequently packed dense mounds of snow in front of his position to conceal himself, provide padding for his rifle and reduce the characteristic puff of snow stirred up by the muzzle blast. He was also known to keep snow in his mouth whilst sniping, to prevent steamy breaths giving away his position in the cold air.
The Soviets' efforts to kill Häyhä included counter-snipers and artillery strikes, and on March 6, 1940, Häyhä was hit by an explosive bullet in his lower left jaw by a Red Army soldier, blowing off his lower left cheek. He was picked up by fellow soldiers who said "half his face was missing", but he did not die, regaining consciousness on March 13, the day peace was declared. Shortly after the war, Häyhä was promoted from alikersantti (Corporal) to vänrikki (Second lieutenant) by Field Marshal Mannerheim.
When asked in 1998 how he had become such a good shooter, Häyhä answered, "Practice." When asked if he regretted killing so many people, he said, "I only did my duty, and what I was told to do, as well as I could." Simo Häyhä spent his last years in Ruokolahti, a small municipality located in southeastern Finland, near the Russian border. Simo Häyhä died in a war veterans' nursing home in Hamina in 2002 at the age of 96, and was buried in Ruokolahti.