What is "Resupply Army"? This feature will allow players to instantly summon the last army they used in a PVP or PVE engagement, for a reduced gem cost, to get immediately back into the action with their next opponent (or PVE Dungeon). Included in the cost: mana refill, the gold cost associated with each individual Minion summon (bundled in for free), and the Battle cost in gold (bundled in for free). If a player's Immortal was knocked out in the previous engagement, the gem cost will also reflect the revive cost.
Where am I able to do this in-game? On the Victory/Defeat combat results screen, a "Resupply" button will appear next to the "Return to Dungeon" button. This cannot be done in Build Mode.
What if I didn't mean to click the Resupply button? When the Resupply button is pressed, players will be presented with an "Are you sure" confirmation window, which will also contain information about what will be replenished if they choose to go through with the transaction. The associated gem cost will only be debited when the player chooses to move forward by clicking the "Find Opponent" or "Play Next Mission"/"Replay Mission" (depending on the win/loss result of the previous PVE battle) button on this confirmation window.
What if I don't have enough gems to Resupply? The Resupply button will still appear, but it will be greyed out.
(Introductory video; Resupply segment begins at 1:26)