Deep Strike
(Rule)Description: During deployment, if all models within a Detachment have the Deep Strike special rule, then the Detachment can be placed in Reserve instead of being deployed as normal. Detachments with the Deep Strike special rule in Reserve can only be issued the Advance Order or March Order.
When a Detachment with the Deep Strike special rule that is in Reserve is activated in any Movement phase other than the first, the controlling player may choose to leave it in Reserve or Deep Strike the Detachment. When a Detachment Deep Strikes, the controlling player places a single model from that Detachment anywhere on the battlefield at least 2" from an enemy model. They then Scatter that model D6". If the model scatters into an area of Impassable terrain or a Structure then that model, and the model's Detachment, is destroyed. If it scatters within 1" of an enemy model, it must be moved the shortest possible distance so it is no longer within 1" of an enemy model.
Once scattered, any remaining models within the same Detachment are placed on the battlefield within 2" of the already placed model. A model cannot be placed in an area of Impassable terrain or overlapping a Structure, not can it be placed within 1" of any enemy model. Any model that cannot be placed in this manner is destroyed. Once a Detachment has Deep Striked, it may complete its activation as normal (i.e., it may move during the Movement phase and/or fire during the Combat phase, etc.).
Some Detachments have both the Deep Strike and Transport (X) special rule. If another Detachment is loaded into the Transport model during deployment, that Detachment is kept in Reserve alongside the Transport model. When the Transport model is set up via Deep Strike, the Embarked model then immediately Disembarks and can then be activated as normal later in the phase.