Four Horsemen of the Apocalypse is the name given by gambling authors[1][2] to the four U.S. Army engineers who first discovered in the 1950s the best playing strategy in the casino game of Blackjack that can be formulated on the basis of the player's and the dealer's cards. The so-called Basic Strategy, which was subsequently refined through the use of computers and combinatorial analysis, loses the least money to the casino in the long term.