Breakthru is an abstract strategy board game for two players, designed by Alex Randolph and commercially released by 3M Company in 1965, as part of the 3M bookshelf game series. It later became part of the Avalon Hill bookcase games. It is no longer in production. The game has been compared to Fox and Hounds, although it shows more characteristics of the Tafl games of the Middle Ages, such as Hnefatafl. As in Hnefatafl, the game features unevenly matched teams with different objectives. The 3M game set includes a board marked with an 11x11 square grid of spaces, twenty silver-colored pieces, a gold-colored "flagship" and twelve gold-colored "escorts". The game is played out as a naval battle analogous to the siege gameplay of Hnefatafl.