For your movement phase movement, you can choose to make it on foot or with the Jet Pack. I thought that they had to use their Jet Pack ability in the Assault Phase, but now looking at the rules, I can no longer find it, as the rules for Jump Infantry is clear that they use normal infantry movement in their Assault move, and Jet Packs are simply a modified sub-form of Jump Infantry, and no mention of this is made in their rules:
Jump infantry can move up to 12" in the Movement phase, instead of the normal 6" move. This is optional and they can choose to move as normal infantry if they wish. When using Jump Packs, movement is not reduced for difficult terrain, and jump pack models can move over other models or obstacles freely. However if they end their move in difficult terrain, they mst take a Dangerous Terrain test.
Ok, so that's the optional movement rules for Jump infantry that is shared with Jet Packs(although it is modified as shown below).
Jump infantry assault 6" like normal infantry. This move is slowed by difficult terrain in the same way as other infantry, because the unit tends to cover the last few yards of a charge on foot.
So Jump infantry can NOT use their Jump packs to assault. This is NOT modified by what is given below for Jet Packs.
Some Jump Infantry are equipped with a specal type of jump pack, referred to as a jet pack. The most frequent users of this technology are the Tau. Jet packs are designed to provide stable firing platforms rather than a means of getting into close combat. Jet packs differ from jump packs in the following ways:
- Note that they are Jump Infantry in every way BUT those I am about to list:
In the movement phase, they only move 6" when using their packs, but are allowed to move 6" in the Assault phase even if they don't assault. This allows them to put more distance between themselves and the enemy.
In the shooting phase, models with jet packs are allowed to fire rapid fire weapons once at up to maximum range, even if the unit has moved. They are also allowed to declare a charge after firing rapid fire weapons.
Note that it says they are allowed to move 6" in the Assault phase, but the prohibition of "assault like normal infantry... slowed by difficult terrain like normal infantry... etc." is not modified in any way. Nowhere does it say you must use the Jump ability during your assault move, or modify the restrictions already given for Jump Infantry.
The older Tau Codex had the prohibition written into the Tau Jet Pack rules, but they are no longer in force. Have we been playing this one wrong all this time???