Core Rules
20. Strategic Reserves
WTC 1 ruling on this section
Abilities, stratagems or other rules that would allow you to be placed into Reserves cannot be used in the 5th battleround in order for it to be destroyed at the end of the battle. If you want to use the Rapid Ingress stratagem on a unit that started the battle in reserves of any kind, in your opponents turn during a game when you had the first turn and therefore they would have the turn at the bottom of the 3rd battleround, then you must declare your intent to do so in the reinforcements step of your 3rd turn and may not spend a Command Point that would stop you from being able to bring in your unit and have it destroyed. Remember that you gain a Command Point at the start of the opponents turn, this can be enough to Rapid Ingress.
20.00Strategic Reserves#
Strategic reserves are units that arrive on the battlefield at different times, either because they were held back during deployment, or because they are using special abilities to reposition themselves.
20.01Placing Units In Strategic Reserves#
Before the battle, in the Declare Battle Formations step, you can select one or more friendly units (excluding FORTIFICATIONS) to place in strategic reserves. Instead of setting up these units on the battlefield during deployment, place them to one side; they are strategic reserves units, and will arrive later in the battle.
Unless otherwise stated, the combined points value of all of your strategic reserves units (including those embarked within TRANSPORTS that are themselves placed in strategic reserves) cannot exceed 50% of your points limit for your battle size.
20.01.02 - Strategic Reserves at the End of the Battle#
At the end of the final turn, units in strategic reserves are destroyed, but they do not trigger rules that apply when a model is destroyed. 
FAQ
Q If I place units in strategic reserves during the battle, can this exceed the 50% of my points limit for the battle restriction as mentioned in Placing Units in Strategic Reserves (20.01)?
Yes. That restriction is applicable before the battle, in the Declare Battle Formations step.
Q Does the limit to the combined points value of my units in strategic reserves only apply until the start of the first battle round?
Yes.
20.02Repositioned Units#
Some rules allow units to be removed from the battlefield and placed in strategic reserves during the battle. Units that use such rules are known as repositioned units. In addition to any other rules that apply to such units (such as where they can or cannot arrive), all of the following rules apply to them:
- If used in the Movement phase, such rules can be used on units that have already moved that phase.
- A repositioned unit that is set up in the same turn in which it made an advance, fall-back or disembark move has still made an advance, fall-back or disembark move that turn.
- When they are removed from the battlefield, any rules that are affecting such units for a specified duration or under specified circumstances continue to affect them while that duration and/or those circumstances apply.
Example: A unit that was within range of an aura ability when removed from the battlefield would no longer be affected by that aura ability if it is no longer within range of it when it makes an ingress move, but a unit that was battle-shocked when removed from the battlefield would still be battle-shocked if it makes an ingress move in the same turn.
20.03Arriving From Strategic Reserves#
To arrive on the battlefield, each strategic reserves unit must make an ingress move (20.04). Unless otherwise stated, they can only do so from the second battle round onwards.
At the end of the third battle round, unless otherwise stated, all strategic reserves units that have not made one or more ingress moves are destroyed, with the following exceptions:
- Units embarked within TRANSPORTS that have made an ingress move during the battle.
- Repositioned units (20.02).
20.04Ingress Move#
- Setup distance
- 6"
- Eligible if
- Your unit is in strategic reserves (excluding units that are embarked within TRANSPORTS that are themselves in strategic reserves)
- Effect
- Your unit is set up as described in Set Up (03.02)
- While moving
- Set up your unit wholly within the set-up distance of one or more battlefield edges and more than 8" horizontally from all enemy units.
- Before the Third Battle Round: While doing so, no models can be set up within your opponent’s deployment zone.
- After moving
- Unless otherwise stated, until the start of the next Charge phase, your unit is not eligible to make any other type of move.