Base Area 112 was a Viet Cong and People's Army of Vietnam base area located in the mountains of Quảng Nam Province southwest of Da Nang near the area known to the Marines as the "Arizona Territory" The base was believed to support the PAVN 21st Regiment, 3rd Battalion, 68B Rocket Regiment, 2nd Battalion, 141st Regiment and command and support units. The operational plan was for Task Force Yankee, an ad hoc unit based around the 5th Marine Regiment, to secure the An Hoa Basin together with the ARVN 1st Ranger Group, the Task Force would then construct a series of fire support bases to support operations west into the Base Area and finally destroy the Base Area.
On 11 December following a preparatory air and artillery strike the engineers of Company B, 3rd Engineer Battalion supported by Company K, 5th Marines landed on Hill 575 8 km southwest of An Hoa Combat Base and established Firebase Lance. On 13 December the engineers supported by Company E, 2/5 Marines established Firebase Pike northwest of Firebase Lance. On 15 December several M-121 Combat Trap bombs were dropped on Hill 558 in an experiment to blast helicopter landing zones in dense jungle. The Combat Trap was only a partial success and Company B, 3rd Engineer Battalion supported by 1st Battalion, 3rd Marines were landed by helicopters to establish Firebase Spear 8 km west of Firebase Lance. On 18 December 3rd Battalion, 3rd Marines was landed on Hill 375 4 km southwest of Firebase Spear and established Combat Operations Base Mace. Having established their operating bases the Marines began patrolling west into the eastern part of Base Area 112, while they found numerous abandoned bunkers, barracks and support facilities no major encounters with the PAVN/Viet Cong occurred and Phase 2 of the operation ended on 31 December 1968
Phase 3
On 1 January 1969 3/5 Marines was landed at Combat Operations Base Javelin and proceeded to bombard Hill 508 however heavy PAVN fire prevented a landing there and the 3/3 Marines was landed on Hill 728 and fought their way to Hill 508 seizing it by 15 January and establishing Firebase Maxwell there. The Marines then proceeded to search the western part of Base Area 112, establishing further firebases as they went and uncovering PAVN base camps and stores. On 15 January an Army UH-1H carrying COL Spark and his command group was hit by machine-gun fire near Firebase Maxwell and crashed killing all on board. On 29 January the 1st Battalion, 7th Marines on Go Noi Island observed a 300 strong PAVN force crossing the Song Ky Lam and artillery fire was directed against them, the PAVN tried to escape to the west but were engaged by Company D, 5th Marines. The fighting continued all night before the PAVN broke contact and the next morning the bodies of 72 PAVN were found. On 10 February Battalion Landing Team3rd Battalion, 26th Marines joined the operation and was landed in the Arizona Territory where they engaged numerous small PAVN units. At the end of February Company L, 3/26 Marines killed 75 PAVN and destroyed two anti-aircraft machine-gun positions. By mid-February Base Area 112 had been largely neutralized and the participating units were needed in the DMZ area, so the operation was progressively scaled back with the 3/3 Marines and the 3rd Marines command group being withdrawn on the 16th and redeployed to Đông Hà Combat Base, followed the next day by 1/3 Marines. After midnight on 23 February PAVN mortars hit An Hoa Combat Base triggering explosions in the ammunition dumps, followed by a sapper attack which was repulsed with gunship and artillery fire. At the same time firebases Maxwell and Tomahawk were hit by mortar and sapper attacks. Due to the withdrawal of participating units from the operation it was decided to withdraw the Marines from the western firebases. On 3 March a patrol from Company M, 3/5 Marines was ambushed near Firebase Maxwell, 3 Marines were killed and 2 of the bodies were left behind as the Company withdrew. The next day the Marines recovered one of the bodies and the following day attempted to recover the other body but were ambushed again losing 2 Marines killed whose bodies also could not be recovered. On 6 March the Marines tried to recover the bodies again but were forced back by PAVN fire, the bodies were later recovered by a reconnaissance team. Firebase Tomahawk was evacuated and closed on 5 March while Maxwell was closed on 7 March.
Aftermath
The operation ended on 8 March 1969. Marine losses were 183 killed and 1,487 wounded, ARVN losses were 100 killed and 378 wounded. The Marines reported 1,398 PAVN were killed and took 29 prisoner. One Marine, Lance Corporal William R. Prom, was awarded the Medal of Honor for gallantry during Taylor Common.
