Russian winterarmy
© Kazbek Basayev/ReutersRussian army soldiers in winter camouflage
Entering Russia would become a "military nightmare" for any army, according to a rating of the hardest countries to invade compiled by Swedish newspaper Svenska Dagbladet. Military might, the size of territory and the difficulty of terrain are among the key factors that determine the country's defensive capability, the paper wrote.

Based on these criteria, the Swedish journalists pointed out that "whomever considers the idea of invading Russia must be prepared to handle all kinds of terrain." The enemy would face desolate mountains, impenetrable swamps, frozen tundra, turbulent rivers, and dark forests in Russia, they said, adding that hot summers and chilling winters would also pose a challenge.

"And then we have the Russians themselves, who for thousands of years, having participated in both large-scale wars and guerrilla warfare, gained a lot of experience," the article said.

The conclusions made by Svenska Dagbladet are backed by Russian history itself, as the country has never been conquered since the creation of a centralized state in Russia in the early 15th century. The Russians have thwarted all attempts to invade their land, defeating among others the armies of French Emperor Napoleon in 1812 and Nazi dictator Adolf Hitler in 1941-45 - who were both considered unstoppable at the time.

Switzerland and New Zealand also made it into the paper's rankings. Despite having a rather small military of just 150,000 troops, the Swiss state remains a hard nut to crack due to it being surrounded by the Alps. It also has a lot defensive facilities, as well as bridges and roads, which could be blown up to hamper the aggressor's advance, the article read.

Conquering New Zealand would be problematic from a logistical point of view, the authors said. The island state is located more than 2,000km from the nearest large landmass, Australia, which would make supplying the invading troops with arms and necessities "almost impossible."