Sovereignty mechanics are something that few players ever deal with directly. Even the vast majority of players who participate in the fleet battle over sovereignty don’t actually touch the underlying systems.
The first step in conquering a system is to anchor Sovereignty Blockade Units on 51% or more of the gates in system. These SBUs take five minutes to anchor at which point they can be onlined. Anyone from any corporation or alliance is able to online them at which point they become owned by the corporation of the person who set them to online. The onlining process then takes three hours.
Once online, an SBU can be turned offline instantly and at any time by their owner. This gives rise to the “defensive” SBU, an alliance will SBU their own system forcing attackers to blow up the SBUs before they can begin. If attackers try, the defenders can simply turn off the SBUs whenever convenient, blocking the attackers from continuing until new SBUs come online three hours later.
Once SBUs are online on 51% or more of the gates, the system becomes vulnerable. When the system is vulnerable, the game will look for a station and an online infrastructure hub. If it doesn’t find at least one of them owned by the same alliance that owns the Territorial Claim Unit, the TCU becomes vulnerable and can be blown up causing sovereignty to drop in the system. Once the TCU is dead, the attackers must take down all SBUs at which point they can online their own TCU. It takes eight hours to online and can be destroyed during that period. There can only be one TCU onlining per corporation, but there is otherwise no limit on how many can be onlining at one time.
Most of the time though, there will be an infrastructure hub and sometimes a station to go with it. An infrastructure hub requires a freighter to anchor and cannot be done while the system is vulnerable. Before you can attack the TCU, these must be killed and captured respectively.
The ihub and station both have similar mechanics, but with slight differences. The defender is able to set a fixed time they want it to come out of reinforced at, and are guaranteed to get that time plus or minus three hours. At 25% shields they go into their first reinforcement timer, they come out at 0% shields. When shot again, they go back into reinforced mode at 50% armor and come out at 25%. After that the ihub will be destroyed, and the station will be captured by the corporation that fires the final shot.
Besides the fact that ihubs explode at the end, the major difference is that the timers are determined differently. Ihubs will come out at the requested timer(+/- 3 hours) plus 24 hours, while stations are plus 48 hours.
Not counting the initial reinforcement, these timers create a possible five or six fights depending on the circumstances and luck. (It’s possible for the station and ihub to line up for one of them) If the defenders win a single timer, they can reset that structure’s part in the system to zero, kill the SBUs, replace the ihub if it was lost, and reconquer the station if it was previously captured.
Once the ihub is destroyed and the station is captured, the attackers can destroy the system’s TCU and begin placing their own. If they manage to get a TCU online, they become the defender and will generally place their own ihub to fully secure the system.