Stalwart units can ignore the first Morale result (flag) rolled against them if they choose.
Stalwart units can also counterattack if they choose (see page 21).
Unlike other keywords, any unit can gain the Stalwart keyword under the right conditions. If a defending unit is adjacent to two friendly units, the defending unit automatically gains the stalwart keyword until that unit is no longer adjacent to two friendly units.
In the following example, Unit B is stalwart because it is adjacent to two friendly units. Unit A is not stalwart because it is only adjacent to one friendly unit. Unit C is stalwart since Maege Mormont (Lady of Bear Island) has the stalwart keyword on her Commander card.
Stalwart can be granted by Keyword Abilities, Leadership Card effects or, typically, by being adjacent to two friendly Units. Being Stalwart allows both Ranged and melee Units to choose to ignore the first Morale (black flag) result rolled against them in an attack, and also to counterattack against the same melee attack as long as they are not eliminated or forced to retreat (by a second Morale result, for example). Units are either Stalwart or not Stalwart, so that even if Stalwart is triggered in multiple ways (such as by the Keyword and by being adjacent to two friendly Units) it only ever allows Units to ignore a single Morale result and/or counterattack once.