Over 40-million people are now registered for the team-based action game World of Tanks.

In terms of active users, World of Tanks developer Wargaming¬†claims that the titles’s Russian server at one point had 500,000 simultaneous players. Which proves my long-held financial theory that Russia should move to a tank-based economy.

The tank game is a popular free-to-play team-deathmatch armored-vehicle battler set during World War II.

This is another example of a developer finding massive success with the free-to-play model. Gamers can sign up for a free account and then either grind away for hours to earn upgrades or pay for improvements via in-game transactions.

Wargaming hopes to expand its reach in this sector of the market with airplane and naval spins on the World of Tanks model. World of Warplanes, the dogfighting game, is in closed beta now. World of Warships, the naval battle title, is still in development. Gamers can follow those titles on the company’s central hub Wargaming.net.