The official rulebook gives three basic strategy tips for the classic rules:
Players should control entire continents to get the bonus reinforcement armies.
Players should watch their borders for buildups of armies that could imply an upcoming attack.
Players should build up armies on their own borders for better defense.
Holding continents is the most common way to increase reinforcements. Players often attempt to gain control of Australia early in the game, since Australia is the only continent that can be successfully defended by heavily fortifying one country (either Siam or Indonesia). Generally, continents with fewer borders are easier to defend as they possess fewer points that can be attacked by other players. South America has 2 access points, North America and Africa each have 3, Europe has 4, and Asia has 5.
Generally, it is thought advisable to hold Risk cards until they can be turned in for maximum reinforcements. This is especially true earlier on in gameplay, because extra armies make a greater difference in the beginning of the game. Eliminating a weak player who holds a large number of Risk cards is also a good strategy, since players who eliminate their opponents get possession of their opponents' Risk cards. In this case, trading in Risk cards earlier may help acquire the necessary troops. If the conquering player has six or more Risk cards after taking the cards of another player, the cards must be immediately turned in for reinforcements until the player has fewer than five cards and then may continue attacking.
"Turtling" is a defensive strategy where a player who feels vulnerable tries to become too expensive to be removed while remaining a threat to harass other players. The objective of this strategy is to avoid defeat. A player using this strategy might remain in the game all the way to later stages and then mount an attack on the weakest player and start a chain elimination to remove one player after another to win the game. The player who uses this strategy is called a Turtle. The term was popularised in Real-time Strategy games where a player creates a defensive perimeter or a "Turtle Shell" around the base of operations. Solutions to counteract this strategy using cooperation have been proposed.
Several computer and video game versions of Risk have been released as Risk, starting with the Commodore 64 edition in 1988 and the Macintosh edition in 1989. Since then, various other editions have been released for PC, Amiga, Sega Genesis, PlayStation, PlayStation 2, and Game Boy Advance. In 1996 Hasbro Interactive released a PC version of Risk that included a new variation on the game called Ultimate Risk, which did not use dice but rather implemented the use of forts, generals, and complex battle strategies. Risk II for PC and Mac was released as a 2000 video game which includes classic Risk as well as board and gameplay variations. In 2010, Pogo.com added a licensed version of Risk to its library of online games. An Xbox Live Arcade version of Risk called Risk: Factions was released on June 23, 2010. It includes classic Risk as well as a factions mode where players can play as Zombies, Robots, Cats, Soldiers, or Yetis.
As of August 6, 2014, Hasbro and Ubisoft have announced a new Risk game to be released in Fall 2014, on PS4 and Xbox One, as well as Xbox 360 and PS3. "Risk will feature an online league play, modern armies, and 3D battlefields. The 2010 rules are the standard set, but players can choose rule modifiers and configurable win variants."
An official licensed iOS app, "RISK: The Official Game", developed for the iPhone, iPod Touch, and iPad by Electronic Arts, was released on July 16, 2010. Although the iPad version (Risk HD) has to be bought separately from the iPhone version (Risk), local link up allows games to take place across versions. A maximum of 6 players can participate. If only one iOS device is available, the 'pass and play' mode allows several players to take part in a multi-player game.