The Four Horsemen of Blackjack

The Four Horsemen of Aberdeen were four United States Army soldiers, Roger Baldwin, Wilbert Cantey, Herbert Maisel, and James McDermott, who in the 1950s worked out the first accurate basic strategy for blackjack. Using mechanical desk calculators rather than modern computers, they spent a long stretch grinding through the math by hand, then published their results. Their pioneering work laid the mathematical groundwork for everything that came after in beating blackjack.

Who were the Four Horsemen?

The Four Horsemen were four young men serving in the United States Army, stationed at the Aberdeen Proving Ground in Maryland during the 1950s. Their names were Roger Baldwin, Wilbert Cantey, Herbert Maisel, and James McDermott. They were not professional gamblers or famous mathematicians but soldiers with a shared aptitude for numbers and a curiosity about whether blackjack odds could be pinned down precisely. Working in their spare time, they pooled their mathematical talent to attack a problem no one had solved rigorously before: what is the mathematically best way to play every possible blackjack hand? The nickname came later, honoring the four of them together, and the town of Aberdeen where their landmark effort took shape while they wore the uniform.

How did they compute basic strategy by hand?

Their achievement is staggering because they had no access to the powerful computers later players would use. Instead they relied on mechanical desk calculators, the adding machines of the day, and worked through the enormous web of probabilities largely by hand. Blackjack has a vast number of card combinations to consider, and evaluating the best decision for each one meant an immense amount of tedious, careful arithmetic. The project consumed a great deal of time and demanded relentless accuracy, since a single error could corrupt the results. Yet they persevered, methodically calculating how each player decision, whether to hit, stand, double, or split, affected the odds against every dealer upcard. The result was the first genuinely accurate basic strategy, produced through sheer human effort and mathematical discipline.

What is basic strategy?

Basic strategy is the set of mathematically optimal decisions for every blackjack hand, given your cards and the dealer's visible upcard. It tells you exactly when to hit, stand, double down, split a pair, or surrender, based purely on which choice loses the least or wins the most on average. The Horsemen were the first to compute this correctly, and their work established the foundation every player uses today. Following basic strategy does not let you beat the house on its own, but it shrinks the house edge dramatically, to roughly half a percent under good rules, compared with the much larger edge a casual player faces by guessing. It is the single most valuable skill in blackjack, and it is the platform on which card counting later added its extra edge.

How did they share their findings?

The Horsemen published their results so others could use them, giving their work lasting influence. In 1956 they presented their findings in a respected statistics journal, lending academic credibility to what might otherwise have been dismissed as a gambling curiosity. They followed this with a book that laid out their strategy for a general readership. Publishing mattered enormously. It meant their carefully computed strategy was not locked away but available for study, verification, and improvement. Their paper and book put accurate blackjack strategy into the record, where later analysts could confirm and build upon it. Without that decision to share, the field might have developed far more slowly. Their willingness to publish turned a private side project into a public foundation for the entire study of the game.

How did their work influence Edward Thorp?

The Horsemen's work was the direct springboard for Edward Thorp, the man usually called the father of card counting. Thorp studied their basic strategy and used it as the starting point for his own research in the late 1950s and early 1960s. Where the Horsemen had established the best way to play a hand in isolation, Thorp went further, using early computers to ask how the odds shifted as cards were removed from the deck, which led him to counting. In a real sense, the Horsemen built the foundation and Thorp built the next floor. His 1962 book Beat the Dealer, which proved blackjack could be beaten, rested squarely on the accurate strategy they had computed by hand years earlier. Progress in blackjack has always been cumulative, and it started with them.

Why were their calculations so difficult?

Several factors made their task extraordinarily hard, and appreciating them shows why the achievement is so respected.

• No computers: they used mechanical desk calculators and manual arithmetic, so every probability had to be worked out slowly and checked carefully.
• Vast combinations: blackjack has an enormous number of hand and upcard situations, each needing its own analysis.
• No prior template: nobody had solved the problem rigorously before, so they had to design their own methods as they went.
• Spare time only: they were serving soldiers, fitting the work around their military duties rather than a research budget.

How were they finally recognized?

For years the Four Horsemen were known mainly to blackjack historians and serious students of the game, their names less famous than Thorp or the MIT team they helped make possible. That changed when they were inducted into the Blackjack Hall of Fame, an honor that recognizes the most important contributors to the game. Their induction formally acknowledged what insiders had long understood: that the entire edifice of beatable blackjack rests on the accurate basic strategy they were first to compute. The recognition was fitting for four men who sought no fame, took on a hard problem out of curiosity, and produced work that has stood the test of time. Decades on, the strategy they calculated by hand still closely matches what modern computers confirm as correct.

Why do they still matter to players today?

The Four Horsemen matter because every blackjack player who uses basic strategy, which is every player who wants a fair shot, is standing on their shoulders. The strategy charts sold in gift shops, printed on cards, and memorized by counters all descend from their pioneering calculations. Their story also carries an honest and encouraging message. It shows that a real edge in blackjack comes from rigorous mathematics and patient discipline, not from luck, superstition, or betting gimmicks. They cut the house edge to around half a percent through careful analysis, and that remains the single biggest improvement any player can make before ever thinking about counting. Learn basic strategy first, play it flawlessly, and you honor the work of four soldiers who solved the game the hard way.

Frequently asked questions

Who were the Four Horsemen of Aberdeen?

They were four United States Army soldiers, Roger Baldwin, Wilbert Cantey, Herbert Maisel, and James McDermott, stationed at the Aberdeen Proving Ground in Maryland during the 1950s. Working in their spare time, they computed the first accurate blackjack basic strategy and published it, laying the groundwork for later advantage play.

How did they calculate basic strategy without computers?

They used mechanical desk calculators and a great deal of careful arithmetic done largely by hand. Blackjack has an enormous number of card combinations, so the work was slow and demanded relentless accuracy. Over a long period they methodically found the best play for every hand against each dealer upcard.

Did the Four Horsemen invent card counting?

No. They computed accurate basic strategy, the best way to play each hand, but not a counting system. Edward Thorp built on their strategy a few years later, using computers to study how removing cards shifts the odds, which led to card counting and his 1962 book Beat the Dealer.

Were the Four Horsemen ever honored?

Yes. They were inducted into the Blackjack Hall of Fame, formally recognizing their role as the pioneers who first computed accurate basic strategy. Though less famous than Thorp or the MIT team, they built the mathematical foundation on which those later, better known advantage players depended.