There is only one corps in the U.S. Army that fights as a corps, and that is never more apparent than when America's First Corps is in a warfighter exercise. Warfighter Exercise 20-3 (WFX 20-3) officially began Feb. 5, 2020, but preparation for the command post exercise began shortly after the new year as camouflage nets and tents went up, spider-webs of power lines and network cable were laid down, and validation and communication exercises tested equipment throughout the latter half of January. By the time Lt. Gen. Randy George took command of First Corps on Feb. 4, 2020, the stage had been set for a simulated force-on-force conflict, the likes of which America hasn't seen since the Vietnam War. Whereas the other two corps in the U.S. Army focus training on counter-insurgency operations in the Middle East, First Corps is prepared to deploy into the Pacific Region with multiple divisions and brigades in tow, fighting in a coordinated and comprehensive effort against a similarly-sized enemy with near-equal capability. In the simulation, artillery fire is exchanged, special forces on both sides dive deep into enemy territory, and brigades fight brigades on the field of battle. The winners of these virtual, large-scale ground combat operations are determined by multi-domain strategy, decisiveness and training, rather than overwhelming firepower. On the opposite side of the field, the Mission Command Training Program of the Combined Arms Center controls the opposing forces putting First Corps through its paces, even going so far as to contract media role-players to literally question leadership on every tactical decision. The Combined Arms Center also sends observer-controllers/trainers for the various staff sections. These OC/Ts can provide valuable insight into the scenario; advise on tactics, techniques and procedures; and take information back to the MCTP to provide a human angle that keeps the CPX from devolving into a video-game style AI battle. WFX 20-3 presented an additional challenge for the First Corps staff as LTG George began the command post exercise on his first day of command. While he had been able to influence some changes during the preparation for the exercise, every day of the Warfighter was an evolving process as staff and subordinate commanders alike adjusted to shifts in the battle rhythm, a new operational center layout, and the new priorities of a new commanding general. While the simulation part of the exercise ended Feb. 13 -- just in time for Valentine's Day -- there's no real rest for First Corps or all the other units involved in the exercise. From the 18th Airborne Corps playing the Coalition Forces Land Component Command from Fort Bragg, N.C., to the 25th Infantry Division participating remotely from Hawaii, or the 40th Infantry Division of the National Guard that mobilized on Joint Base Lewis McChord for WFX 20-3, a long list of lessons learned and recommendations for next time will be accumulated. Units like the 42nd Military Police Brigade, 555th Engineer Brigade, 17th Field Artillery Brigade, 593rd Expeditionary Sustainment Command and 26th Maneuver Enhancement Brigade will have their own inputs as well, even as they join the Soldiers of higher commands to recover tents and equipment as soon as there is a break in the rain -- but on JBLM, it never stops raining for long, and in First Corps, the Soldiers never stop training for long. Planning for the next Warfighter Exercise began before WFX 20-3 was even finished.