TOKYO, 22 Sep - All the teams at this Rugby World Cup, apart from Fiji, Tonga and Uruguay, score most of their tries from lineouts.
Any lineout close to the try line presents a perfect attacking opportunity. In order to strengthen their defence, the defending team are unlikely to contest the lineout: jumping requires three men (two lifters and the jumper) and when they are competing in the air they cannot defend the subsequent maul.
Because of this numerical inferiority, if they were to lose the lineout - and most of the time the defending team will lose it - the short-handed defence will immediately get driven back in the maul and over their own try line.
When teams do not compete at the lineout and choose to defend the maul instead, they try and drive the attack backwards as soon as the jumper’s feet hit the ground.
If you look 34 seconds into the video above, you can see how the Scottish tight-head prop, WP Nel, crashes in as soon as Ireland's James Ryan hits the ground. Scotland are trying to push Ireland out of the field of play. If they cannot do that, they will want to restrict Ireland's attacking options by pushing the maul towards the touchline; if they manage that, they only need to defend one side of the maul and can focus their defensive efforts across the rest of the pitch.
In this case, Ireland ride the push to the line. They keep driving forwards and wait for the Scottish defenders to swing around the outside. Eventually Greig Laidlaw is left as the last man between the Irish pack and the Scottish try line. Naturally he cannot stop the drive on his own and Rory Best scores.
One minute 26 seconds into the video above you can see the Italians doing something very similar.
Namibian captain Tjiuee Uanivi competes by himself at the front of the lineout. His plan is to disrupt the catch or steal a very poorly thrown ball.
When Italy win the ball, Namibia do exactly what Scotland did, driving Italy towards the touchline to reduce the amount of space they need to defend. Italy resist this pressure and drive straight. Namibia's players swing around the outside, and before long there are not enough Namibian defenders to stop Jake Polledri’s drive to the line.
Hookers are the joint highest try scorers at this World Cup with six, and five of their tries have come from mauls. The lineout is almost certainly going to be the source of most tries at this tournament and teams will need to learn from what they have seen during this first weekend or they will keep struggling when they concede penalties, which can be kicked to the corner.
Will teams give up trying to force the opposition to the sideline and accept that they need to defend both sides of the maul, or will they persevere with that tactic in the hope that they eventually get it right?
The first chance to see whether teams will change their maul defence tactics will come when Georgia face Wales on Monday night. Both teams will be wary of the other’s pack and we should see plenty of mauling, but how will the defending team respond, and will this continue to be the hooker’s World Cup?