As the type of operation is Defensive, you must participate in defensive battles, i.e., battles in zones controlled by Windurst.
You still get the EXP/Limit Points and Allied Notes from Campaign as well as the reward from the Campaign Op.
This mission can be completed regardless of zoning, time taken, or otherwise. So as long as you assess the required experience in one or more campaign battles.
A notice saying you have completed the mission will appear in the message window with Experience and Allied Notes upon satisfactory completion of the objectives.
Beastman Confederate forces are now planning full-scale seiges on federal strongholds within Windurst territory. Join the battle along the Sarutabaruta and Aragoneu fronts and assist our mercenaries of the Cobra Unit in defending these key strategic points.