What is rush defense in rugby?

Answer 1

When implementing the 'Man-on-Man' defensive system, a defending player marks his opposite number whenever possible. So for example, the defending fly-half will mark and pursue the opposition fly-half off a scrum. The goal is to quickly and directly attack the opposite number in order to pressure them into a mistake or to quickly smother and disrupt any offensive patterns.

The Man-on-Man Rugby defense serves as the basis for the 'blitz' or 'rush' defense (many claim they are the same or would be if done properly) and can be brutally effective when implemented well

If the opposition offense brings an extra man into the attacking line, the defenders continue to cover their opposite man (not necessarily their opposite number) and continue to move up together. As a result of this marking pattern, the last outside player in the attacking move is unmarked when an extra man is brought into the line. In order to contain the outside man, the defense will often try and force the offense to the sideline while the fullback (typically) will fill in the defensive line and mark the once-uncovered outside man in the attacking line.