Red defence

Red defence has two meanings in the Planetarion universe. The first refers to asteroid stealing and is used to attempt to reduce an attacker's roid cap. The second is in reference to rounds that involved subversion as a ship type.

Nowadays, red defence has gone all but extinct.

Reducing roid cap

Prior to PAX, one could only gain the maximum number of roids by sending a fleet that was in proportion to the target, discouraging overkill. If defense was running out, players could instead attack their own alliance, thereby increasing the size of the attacking fleet, reducing overall roid cap.

During the PAX-era, the roid cap formula was changed. Currently, every attacking fleet gets a percentage allocated to it according to the value of the fleet as compared to that of the value of all the attackers. Each attacker then gets a chance to steal roids, if there are any pods in the fleet. If there aren't, the fleet does not cap anything. This mechanism can be used to reduce overall cap by piggybacking an attacker with fleets without pods. Unlike pre-PAX, however, this must be done by players in different alliances, because it's no longer possible to attack your own galaxy or alliance, nor the alliances you're NAP'ed with.

Subversion

In the context of Subversion, red defence was designed to exploit an interesting (and unintentional) quirk of Subversion. Subversion was a kind of "Stealing EMP", whereby if an enemy ship was attacked by a subversion ship, it would be converted to firing on its own side. However, as part of the combat engine, any unit that had been subverted could no longer be destroyed.

This quirk was soon exploited by Zikonian players, who would send an attacking fleet consisting of Subversion ships, in addition to a Defending fleet. The defnding fleet would contain ships that would arrive, only to be subverted and then fire on the 'real' defenders. This was especially effective when Xandathrii ships were used, because they were traditionally easily stunned and inflicted high damage, and when subverted became indestructible, offsetting their major drawback.

This 'abuse' of the combat system lead to many instances in which defenders were wiped out and ultimately lead to the removal of subversion following round 12 and the re-introduction of stealing for Zikonians.