Stahlberg finished in 6th place at the 1952 Stockhom Interzonal tournament. This earned him a place in the Candidates match at Zurich.
Despite finishing in last place (15th) in a field of tough competition, he did manage to win both games against 10th place finisher, Averbach . As Black in round 12, he plays a Tarrasch variation of the French Defense and is allowed some counter play on the Queen’s side. Oddly enough this game wasn’t as well annotated by Bronstein in the book and I found this following position peculiar of a missed win for White on move 44: ( diagram)
Had Averbakh simply played 44. Re8+ Nf8 ( forced) 45. Ne6 I felt this was winning for White. Having missed that, White instead plays 44. Re7 and allows Stahlberg to wiggle out and actually gain the upper hand.
When they flipped sides in round 27, playing an older line of an Indian Defense, he draws his opponent to over extend himself. This gives him an opportunity to play take over control over the light squares. Averbach overextends the pawns on both sides and this creates longer term structural weaknesses for the endgame. Once the Queens are off the board, Stahlberg demonstrates a nice 2R+Ps endgame with active rooks that takes advantage of the holes created in the middle game.
His third win was against Kotov ( yes, the Think Like a Grandmaster author) in round 2. Here he plays a signature Knight maneuver that has both Smylov and Bronstein puzzled for a good refutation. In this position on Black’s move 11, he plays 11…Nf8 before ( see diagram below) castling to get his knight to e6 as a sharp variation for an other wise quiet semi-closed position.
By the time he encounters Bronstein in round 22, his opponent has had a chance to observe this peculiar knight move and prepare a line. In response to the Nf8-Ne6 line, Bronstein tries a King’s side attack initiated with an h-pawn.
Smylov as Black in round 19, leading the pack, decides to play for a safe draw in a very bookish mainline Slav. He didn’t want to take any chances. Likewise, Reshevsky in round 21, plays a rather Dull line of a King’s Indian to avoid any sharp lines for Stahlberg and draws in a 3 fold repetition.
There were several GM draws in 30 moves or less against Stalhberg. 10 draws in all for a total of 8 points gained for the event.
After the Candidates match of 1953, he went on to Umpire in the World Championship matches between 1957 and 1963 ( Botvinnik and Petrosian). He published several chess books ( 10 in all) , some of them originally in Swedish. I kamp med världseliten (In Battle against the World Elite, 1948, 1958); Schack och schackmästare (Chess and Chess Masters, 1937,1959);Strövtåg i schackvärlden (Excursions in the World of Chess). They seemed to be a collection of either his games or those of his predecessors.
In 1967 he travelled to Leningrad to take part in an international tournament but died of a heart attack before playing his first game.