Rugby union is a contact sport that consists of two teams of fifteen players. The objective is to obtain more points than the opposition through scoring tries or kicking goals over eighty minutes of playing time. The play is started with one team drop-kicking the ball from the halfway line towards the opposition. The rugby ball can be moved up the field by either carrying it or kicking it. However, when passing the ball it can only be thrown laterally or backward. The opposition can stop players moving up the field by tackling them. Only players carrying the ball can be tackled and once a tackle is completed the opposition can compete for the ball. Play continues until a try is scored, the ball crosses the side line or dead-ball line, or an infringement occurs. After a team scores points, the non-scoring team restarts the game at the halfway with a drop kick toward the opposition. The team with the most points at the end wins the game.
Typical gameplay
A typical passage of rugby union takes the following form. Unlike rugby league and gridiron football, possession of the ball in rugby union is contestable at any time by both teams – there is no separate 'offense' and 'defense'. The team which has possession of the ball at any given time will normally try to keep it, while the other team will try to recapture it, or at least deny the team in possession the chance to attack and/or force it to kick the ball away or commit an error. One team will initially gain possession of the ball, either from the kick-off, a restart kick or a set piece (scrum and line-out). The need to maintain possession means the team with the ball will usually seek to progress towards the opposition by running forward while carrying the ball; although if there are few opportunities to attack they may choose to kick the ball forward, from the hand, usually giving it back to the opposition but in a position from where it will be difficult to attack. The ball may be thrown from one player to another (passing) but must not be thrown forward, that is towards the opposition dead-ball line. Any teammate ahead of the ball-carrier is offside and must not interfere with play. So American football-style blocking is forbidden, although tackling or obstructing a player who does not have the ball is against the laws anyway, whether or not the tackling player is offside. The team not in possession attempts to stop the ball-carrier by grabbing and bringing them to ground (a tackle). A tackled player, once having been brought to ground, must immediately pass or release the ball, allowing the two teams to contest possession of the loose ball; if the attacking player is tackled but the tackler releases the ball carrier the ball carrier may get up and continue the play. Play does not stop unless there is an infringement of the Laws, the ball/ball-carrier leaves the field of play, the ball becomes unplayable after a tackle, or the attacking team scores points by either touching the ball over the goal-line (a try) or drop-kicking the ball over the crossbar. If the ball or ball-carrier goes into touch (out of the field of play), the game restarts with a line-out. If the game stops due to an infringement, play restarts with either a scrum, free kick or penalty kick (depending on the nature of the infringement) to the non-infringing team.
Running
Players can run with the ball in any direction they want. However they cannot use a teammate to obstruct the opposition. This occurs when they run around or into one of their own players and in the process prevent a defender from tackling them. Defending teams can also run anywhere they want as long as they do not start from an offside position. Offside lines are behind the last foot at a ruck, maul or tackle or five and ten metres back from scrums and lineouts respectively. If the ball is kicked, players from the kicking team cannot run forward until they have been passed by the kicker or someone behind the kicker.
Forwards tend to run straight and hard at the opposition, while the backs run at gaps between players or use speed and guile to run around them. In modern games of rugby some backs can be as big as forwards and attempt to break through the defensive line using brute force and many forwards possess the running skills of backs. Players run straight at the opposition with the aim of either breaking the tackle or getting forward momentum from which to set up another attack. If they are close to the try line they can drive in low to aid grounding the ball. Players can also try to break through tackles by spinning after making contact or by using the hand not carrying the ball to fend (push) off the defender.