The fact that they are doing their job is not interesting or relevant. What's interesting and important is the specific scenario they are forced to consider, and what it says about the state of the country.
Military think-tank identifies a situation for which where there is no modern war plan, a situation which could possibly happen if global circumstances change.
Think-tank writes up a detailed notional scenario describing the world in which that situation could occur and hands it off to military leaders.
Military leaders present it as a war game to their staff, assign different units to different sides.
Military staff proceeds to generate plans to win their side of the 'war', possibly executing maneuvers in mock battles or training events, and write up lessons learned and battle tactics and strategies.
These write ups are compiled into "war plans" and codified.