Hippopotamus Defence

The Hippopotamus Defence is a name for various irregular chess opening systems in which Black moves a number of pawns to the sixth rank, often developing pieces to the seventh rank, and does not move any pawns to the fifth rank in the opening. 
Evaluation.
Chess master and author Fred Reinfeld once stated of it that "any expert player would dismiss Black's position as lost." Grandmaster Reuben Fine, one of the world's strongest players in the 1930s and 1940s, instructing his readers how to deal with such "Irregular Openings", wrote that "once a plus in development or center is set up, a well-conducted attack will decide."
Reinfeld, who died in 1964, might have been surprised to see Black employing the same system of development successfully in the 1966 world championship match. There, Boris Spassky employed the same set-up, dubbed the "Hippopotamus" by commentators, in the 12th and 16th match games against World Champion Tigran Petrosian. In both games Spassky developed his bishops to b7 and g7, and his knights to d7 and e7. (See diagrams.) Both games ended in draws. (See illustrative games below.)
In employing this system against Petrosian, Spassky was likely inspired by the Slovak International Master Maximilian Ujtelky, who had been experimenting with similar openings for several years. Ujtelky's game as Black against Spassky at Sochi 1964, in which he played the same setup Spassky later adopted against Petrosian, is given below. Ujtelky played even more provocatively in some other games, such as against the Soviet International Master Rashid Nezhmetdinov in the same tournament (see diagram at right). Nezhmetdinov sacrificed pawns on moves 26, 36, and 41, a knight on move 45, and a bishop on move 47 – and lost in 75 moves. Amatzai Avni, an Israeli FIDE Master and psychologist, has written of Ujtelky's play:
Basically, Ujtelky was provoking his opponents to the extreme and was waiting for them to have a nervous breakdown. Sometimes he was slaughtered, at other times his scheme paid dividends.
International Master Andrew Martin has written of the Hippopotamus, "The idea is that Black develops within his first three ranks at the beginning of the game. He will construct a solid, stable yet flexible position, wait to see what White is doing and react accordingly."
In his book on the Hippo Attack & Defence, Eric Briffoz wrote:
"The Hippo somehow combines the benefits of the Owen defence (1… b6), together with the benefits of the Modern Defence (1…g6). While the Owen focuses on mainly controlling the central white squares d5 and e4, the Modern seeks to control the black ones on e5 and d4… "
<br>Grandmaster Tiger Hillarp Persson has written: [T]he Hippo lies low in the water. It looks almost ridiculously passive and many theoreticians consider the Hippo to be a peaceful, almost meek animal. But nothing could be further from the truth. On closer scrutiny the animal, the position, and the statistics look almost entirely different. The Hippo is a fierce animal; ready to crush anyone who gets too close. Vlastimil Hort, Igor Glek and Mihai Suba are among the grandmasters who have employed the Hippo, and Kiril Georgiev has used it as an anti-computer line. As alluded to above, IM Andrew Martin wrote a book, "The Hippopotamus Rises: The Re-emergence of a Chess Opening", about that opening in 2005. See review here.
The term "Hippopotamus Defence" was also used by the English amateur J. C. Thompson to describe a system of his devising, where Black played c6, d6, e6, and f6; developed his knight, via h6, to f7; and did not necessarily fianchetto his bishops. As White, Thompson played the mirror-image of this. Thompson advocated this system in his 1957 book "Hippopotamus Chess Opening". However, Martin writes that "frankly, his ideas have little value today". 
Illustrative games.
Raymond Keene and G. S. Botterill remark, "Such strength as the Hippopotamus has derives from the resilience of a cramped but not compromised position, and the dangers White will run of 'trying too hard' and being tempted into a rash advance." They cite this game as an example of that phenomenon.
This was one of Miles' last games, and posthumously won him the "Game of the Season" award.