Any ship can choose the Intercept mission in order to attempt to move to the same point as another starship. To do so, the player must be able to "see" the target ship on the starmap; if you lose "sight" of the other vessel, it becomes an invalid target and the intercept fails.
Intercepting takes place during the Intercept phase of the movement stage of the Host Order. The three major movement phases of the Host are:
If you are intercepting and your target isn't, your target will move in one of the earlier movement phases ("Move Tow" or "Move Most"), and you will move toward it in the "Move Intercept" subphase.
Since all Hyperjumps take place during the "Move Most" phase, intercepting ships can successfully target them for intercept, if the destination location can be scanned. However, since the Firecloud Chunnel takes place after all movement, intercepting a Chunnelling starship will normally leave the intercepting ship at the target's pre-Chunnel location. Likewise, as Cloaking takes place before any movement, a successful cloak will generally cause the intercept attempt to fail — but a failed or interrupted cloak leaves the target starship vulnerable.
It is significant to note that a ship with a failed Intercept mission will not move at all, regardless of waypoint settings, but a ship set to Warp 0 and Intercept will have its waypoint set to the last recorded sighting of the target at the beginning of the next turn.
If the targeted ship has cloaked, moved via Chunnel, or was not visible to the player at the beginning of the turn, the target becomes invalid and the Intercept mission will have no effect.
In games where Classic Intercept is used, intercepting ships move in Ship ID sequence. This can make it rather difficult to successfully intercept starships with a high Ship ID. It is also non-intuitive. It is, however, the version of Intercept that was used in VGA Planets and remains the system in all Classic games.
In Nu year 108, Planets.nu released a new version of Intercept called Chained Intercept. The idea behind it was to make the Intercept Mission operate in a more intuitive manner. This feature was made available for Custom Games at that time.
For Standard games generated after January 1, 2021 (Nu year 121), Chained Intercept is used. (Classic Intercept will continue to be used in Classic games and will be optional in Custom games). In games where Chained Intercept is active, starships will take turns following each other; like the links in a chain, the first interceptor will move, then the second, and so on. If you are intercepting a ship that is intercepting another ship, you will wait for your target to move before you pursue them. Likewise, any ships intercepting you will wait for you to move before they move.
In certain situations where chained interceptors form a loop, one ship will be designated to go first. The lead ship is decided by two factors: