The first echelon of the 1st Marine Division planning group had its preliminary briefing on 19 August, and the tractor elements of the Attack Force were scheduled to sail for the objective area on 9 September. This left an interval of 20 days for most of the Inchon planning—probably the shortest period ever allotted to a major amphibious assault.
Less than one-fourth of the officers and men of the 1st Marine Division staff were on the Mount McKinley when planning commenced. At that time the distribution of the staff was as follows:
| With the 1st Prov Mar Brig in Korea | Aboard USS Mount McKinley in Tokyo | En route by sea to Japan | Total | |
| Div Cdr Section | 2 | 2 | ||
| Asst Div Cdr Section | 2 | 2 | ||
| Chief of Staff Section | 2 | 1 | 1 | 4 |
| General Staff Section: | ||||
| G-1 | 2 | 2 | 1 | 5 |
| G-2 | 2 | 2 | 7 | 11 |
| G-3 | 2 | 2 | 1 | 5 |
| G-4 | 2 | 2 | 2 | 6 |
| Special Staff Section: | ||||
| Adjutant | 4 | 7 | 11 | |
| Air & Air Observers | 2 | 1 | 2 | 5 |
| Amph Trac | [a]1 | [a]1 | 2 | |
| Anti-Tank | [b]1 | 1 | 1 | |
| Armored Amtracs | [a]1 | 1 | ||
| Artillery | [a]1 | [a]1 | [a]1 | 3 |
| Chaplains | [b]1 | 1 | 1 | |
| Chem War & Radiol Def | 1 | 1 | ||
| Dental | [b]1 | 1 | 1 | |
| Embarkation | [b]1 | 2 | 1 | 3 |
| Engineer | [a]1 | |||
| Food Director | 1 | 1 | ||
| Hq Comdr | [a]1 | [a]2 | 3 | |
| Inspector | 2 | 2 | ||
| Legal | [b]1 | 1 | 1 | |
| Liaison | 3 | 3 | ||
| Medical | 2 | 1 | 3 | |
| Mtr Trans | 1 | 1 | 2 | |
| Nav Gunfire | 1 | 1 | ||
| Ordnance | [b]1 | 1 | 1 | |
| Post Ex | [a]1 | 1 | ||
| Pub Info | [b]1 | 1 | 1 | |
| Prov Marshal | [a]1 | 1 | ||
| Shore Party | [a]1 | 1 | ||
| Signal | 6 | 2 | 8 | |
| Spec Serv | [b]1 | 3 | 3 | |
| Sup & Disb | [b]2 | 9 | 9 | |
| Tank | [b]1 | [a]1 | 1 | |
| Total | 33 | 23 | 51 | 107 |
[a] Carried in other Brigade, Division, or Force units.
[b] Additional duty basis; not counted in total.[86]
[86] O. P. Smith, Notes, 54–55.
The Marine planners aboard the Mount McKinley were short on elbow room as well as personnel, time, and equipment. Although it was an advantage to have the planning groups of the Attack Force and Landing Force together, the ship did not provide enough space for both without crowding. Moreover, the already undermanned Marine contingent had to be further reduced late in August by sending several officers to Kobe to meet incoming units. Thus the G-2 section, to cite one example, consisted of only two officers, one of whom was detached on this duty for a week.
“The issuance of and adherence to a planning schedule was utterly impossible,” commented the 1st Marine Division report. “Only by a virtual ‘around the clock’ working day, concurrent ... planning by Attack Force (ComPhibGru One) and Landing Force (1st MarDiv), willing teamwork by both, and especially the amphibious ‘know-how’ of key staff members gained by long experience, was it possible to complete and issue ... plans and orders for a most difficult ... landing operation. The time-space factor denied any coordinated orientation, prohibited even the most elementary rehearsal, made it difficult to distribute orders, and gave subordinate units very little time for formulation and distribution of their plans.”[87]
[87] 1st MarDiv SAR, basic rpt.
Command relationships during the embarkation and assault phases were as follows: