| Naval Forces, Guam | |
| Governor, Guam, and Commandant, | Capt George J. McMillin (USN) |
| Naval Station, Guam | |
| Aide for Civil Affairs to Governor, | Cdr Donald T. Giles (USN) |
| Guam and XO, Naval Station, Guam | |
| CO, Navy Yard, Piti, Guam | LtCdr O.W. Gains (USN) |
| CO, Marine Barracks, Sumay, Guam | LtCol William K. McNulty (USMC) |
| XO, Marine Barracks, Sumay, Guam | Maj Donald Spicer (USMC) |
| Guam Insular Patrol | 1stLt Charles S. Todd (USMC) |
| USS Penguin (AM-33) | Lt J.W. Haviland, III (USN) |
| USS Robert L. Barnes (AG-27) | Lt J.R. Nestor (USN) |
| Navy Hospital, Agaña, Guam | Capt W.T. Lineberry (USN) |
| Japanese Forces | ||
| South Seas Detachment | MajGen Horii | |
| HQ, 55th Infantry Group | 109 | |
| 144th Infantry Regiment | Col Kusonose | 2,925 |
| I Battalion, 55th Mountain Artillery Regiment | 773 | |
| 3rd Company, 55th Cavalry Regiment (+ AT gun platoon) | 96 | |
| 1st Company, 55th Engineer Regiment | 269 | |
| Other Attachments | 734 | |
| Company, 47th Field AA Gun Battalion | ||
| Detachment, Medical Unit, 55th Division | ||
| Detachment, 1st Field Hospital, 55th Division | ||
| Detachment, Water Supply Unit, 55th Division | ||
| 5th Company (+), Maizuri 2nd SNLF | Cdr Hayashi | 370 |
| Southern Attack Force (TF 53) | Rear Adm Richard R. Conolly11 |
| Northern Attack Group (TG 53.1) | |
| Northern Transport Group (TG 53.3) | Capt Pat Buchanan |
| Minesweeping and Hydrographic Group (TG 53.9) | LtCdr G.M. Estep |
| Tractor Group 3 (TG 53.16) | Capt G.B. Carter |
| Southern Attack Group (TG 53.2) | Rear Adm L.F. Reifsnider |
| Southern Transport Group (TG 53.3) | Capt J.B. McGoven |
| Tractor Group 3 (TG 53.17) | Cdr E.A. McFall |
| Minesweeping and Hydrographic Group (TG 53.6) | Cdr R.R. Sampson |
| Corps Reserve Group | Capt H.B. Knowles |
| Carrier Support Group (TG 53.7) | Rear Adm V.H. Ragsdale |
III Amphibious Corps (Southern Troops and Landing Force – TG 56.2)
Force Troops
IIIAC Service Group [shore party and services]
IIIAC HQ&S Battalion (-)
IIIAC Signal Battalion (-)
4th Marine Ammunition Company
IIIAC Artillery
1st (-) and 2nd 155mm Howitzer Battalions
7th 155mm Gun Battalion
IIIAC Rear Echelon
1st Base Headquarters Battalion
1st Separate Engineer Battalion
1st MP Company
3rd Joint Assault Signal Company
5th Field Depot (-)
1st Prov Base HQ, Island Command, Guam
HQ&S Battalion, 1st Prov Base HQ
3rd MarDiv (Reinforced)
3rd Combat Team [Beaches “Red 1” and “Red 2”]
3rd Marines (Reinforced)
25th NC Battalion (-)
Company C, 1st Battalion [engineer], 19th Marines
Company F, 2nd Battalion [pioneer], 19th Marines
Company C, 3rd Medical Battalion
Company C, 3rd MT Battalion
Company C, 3rd Tank Battalion [M4A2]
Battery I [40mm], Light Antiaircraft Group, 14th Defense Battalion
9th Combat Team [Beach “Green”]
9th Marines (Reinforced) [1/9 Division Reserve]
1st Battalion [engineer] (-), 19th Marines
3rd Tank Battalion (-) [M4A2]
Company D, 2nd Battalion [pioneer], 19th Marines
Company G (+ detachment, HQ Company), 25th NC Battalion
Company A, 3rd MT Battalion
Company A, 3rd Medical Battalion
3rd Reconnaissance Company (-)
21st Combat Team [Beach “Blue”]
21st Marines (Reinforced)
2nd Battalion [pioneer] (-), 19th Marines
Company B, 1st Battalion [engineer], 19th Marines
Company H (+ detachment, HQ Company), 25th NC Battalion
Company B, 3rd Medical Battalion
Company B, 3rd MT Battalion
12th Marines [artillery] (Reinforced)
14th Defense Battalion (-)
Reserve Group
HQ Battalion (-), 3rd MarDiv
Company B (-), 3rd Tank Battalion [M4A2]
Engineer Group [shore party]
19th Marines [engineer] (-)
2nd Separate Engineer Battalion
25th NC Battalion
Company B, 2nd Special NC Battalion
Service Group
3rd Medical Battalion (-)
3rd Service Battalion (-)
Detachment, Service Group, 5th Field Depot
2nd Marine Ammunition Company (-)
Attachments
1st Armored Amphibian Tractor Battalion (-) [57 x LVT(A)1]
3rd Amphibian Tractor Battalion (+) [193 x LVT(2)/(4)]
Company A, 10th Amphibian Tractor Battalion [LVT(2)]
IIIAC MT Battalion (-) [60 x DUKW]
1st Prov MarBde
HQ Company, 1st Prov MarBde
MP Company, 1st Prov MarBde (-)
Signal Company, 1st Prov MarBde (-)
1st Prov Replacement Company
4th Combat Team [Beaches “White 1” and “White 2”]
4th Marines (Reinforced)
Engineer Company, 4th Marines
Medical Company, 4th Marines
MT Company, 4th Marines
Pioneer Company, 4th Marines
22nd Combat Team [Beaches “Yellow 1” and “Yellow 2”]
22nd Marines (Reinforced)
Engineer Company, 22nd Marines
Medical Company, 22nd Marines
MT Company, 22nd Marines
Pioneer Company, 22nd Marines
Tank Company, 22nd Marines [M4A2]
305th Regimental Combat Team (USA) [Brigade Reserve]
305th Infantry Regiment (Reinforced)
242nd Engineer Combat Battalion [shore party]
Company A, 302nd Engineer Combat Battalion
Company C (-), 706th Tank Battalion [M4A2]
Artillery Group, 1st Prov MarBde
HQ Detachment, Artillery Group, 1st Prov MarBde
Pack Howitzer Battalion, 4th Marines
Pack Howitzer Battalion, 22nd Marines
305th Field Artillery Battalion (105mm Howitzer) (USA)
Battery C, 1st 155mm Howitzer Battalion
Amphibian Tractor Group
4th Amphibian Tractor Battalion (+) [178 x LVT(2)/(4)]
Companies A and B, 1st Armored Amphibian Tractor Battalion [26 x LVT(A)1]
Company A, 11th Amphibian Tractor Battalion [LVT(2)]
Company C (Amphibian Truck), IIIAC MT Battalion [40 x DUKW]
Antiaircraft Group
9th Defense Battalion (- Seacoast Artillery Group)
Battery A, 7th AA Automatic Weapons Battalion [40mm/.50-cal.] (USA)
IIIAC Medical Battalion (Reinforced)
77th Infantry Division (Reinforced) (- 305th RCT to 1st Prov MarBde)
Divisional Troops
HQ, 77th Infantry Division
Special Troops
HQ Company, 77th Infantry Division
77th Cavalry Reconnaissance Troop
77th Signal Company (- detachments)
77th Quartermaster Company
777th Ordnance Light Maintenance Company (-)
HQ and HQ Battery, 77th Infantry Division Artillery (-)
306th Field Artillery Battalion (155mm Howitzer)
306th Regimental Combat Team
306th Infantry Regiment (Reinforced)
304th Field Artillery Battalion (105mm Howitzer)
132nd Engineer Combat Battalion [shore party]
Company B, 302nd Engineer Combat Battalion
Company B, 706th Tank Battalion [M4A2]
Company B, 302nd Medical Battalion
Battery B, 7th Antiaircraft Automatic Weapons Battalion
307th Regimental Combat Team
307th Infantry Regiment (Reinforced)
902nd Field Artillery Battalion (105mm Howitzer)
233rd Engineer Combat Battalion [shore party]
Company C, 302nd Engineer Combat Battalion
Company A, 706th Tank Battalion [M4A2]
Company B, 302nd Medical Battalion
Battery C, 7th Antiaircraft Automatic Weapons Battalion
Attachments
7th Antiaircraft Automatic Weapons Battalion (-) [40mm/.50-cal.]
302nd Engineer Combat Battalion (-)
302nd Medical Battalion (-)
36th Medical Field Hospital (-)
95th Medical Portable Surgical Hospital
Company A (-), 88th Chemical Battalion (Motorized) [4.2-in. mortar]
292nd Joint Assault Signal Company (-)
404th Ordnance Medium Maintenance Company
| 29th Division (-)1 (Southern Marianas Army Group) | |
| 29th Division HQ | 220 |
| 18th Infantry Regiment (- I Battalion)2 | 1,300 |
| 38th Infantry Regiment | 2,894 |
| 29th Division Intendance Unit | 133 |
| 29th Division Signal Unit | 186 |
| 29th Division Ordnance Unit | 45 |
| 29th Transport Unit | 94 |
| 24th Tank Company | 117 |
| 265th Independent Transport Company | 180 |
| Element, HQ, 13th Division3 | 200 |
1. 50th Infantry Regiment on Tinian.
2. I Battalion on Saipan. Strength further reduced by submarine losses.
3. Advance detachment probably absorbed into other headquarters.
| 48th Independent Mixed Brigade (-) | |
| 48th IMB HQ | 149 |
| 319th Independent Infantry Battalion | 368 |
| 320th Independent Infantry Battalion | 486 |
| 321st Independent Infantry Battalion | 488 |
| 322nd Independent Infantry Battalion | 500 |
| 48th IMB Artillery Unit | 368 |
| 48th IMB Engineer Company | 186 |
| 48th IMB Signal Company | 109 |
| 48th IMB Medical Company | 164 |
| 2nd Company, 9th Tank Regiment | 122 |
| 10th Independent Mixed Regiment (-)* | 1,912 |
| 10th IMR HQ | |
| II Battalion | |
| III Battalion | |
| 10th IMR Artillery Unit (-)* | |
| 10th IMR Engineer Company (-)* | |
| 10th IMR Signal Company | |
| 1st Company, 9th Tank Regiment | 122 |
* I Battalion, an artillery company, and an engineer platoon on Rota.
| 52nd Field Antiaircraft Battalion (- 1st and 3rd Co) | 250 |
| Antiaircraft Unit, 18th Infantry | |
| 45th Independent Antiaircraft Company | |
| 2nd Company, 7th Independent Engineer Regt | 225 |
| 2nd Company, 16th Shipping Engineer Regt | 200 |
| 54th Guard Force | 2,300 |
| 21 coast defense gun companies | |
| 60th Antiaircraft Defense Unit | 259 |
| 217th Construction Battalion | 900 |
| 218th Construction Battalion | 900 |
| Land Reclamation Unit (civilian laborers) | 300 |
| Guam Branch, Southeast Area Air Depot | 100 |
| 263rd Air Group (Hyo Unit) | 800 |
| 521st Air Group (Otori Unit) | 400 |
| 755th Air Group (Genzan Unit) | 700 |
Harmon Field was built on the site of the incomplete Japanese Dededo airstrip north of Agaña. XXI Bomber Command was headquartered there from December and Twentieth Air Force from July 1945. Each of the five US airfields built on Guam was massive compared to the three crude airstrips built by the Japanese.
11 Commander both Southern Attack Force and Northern Attack Group.