9 March—The Navy stays in barracks buildings and has liberty every night with liquor to drink and makes a big row.
We, on the other hand, bivouac in the rain and never get out on pass. What a difference in discipline!
12 June—Our AA guns [manned by the Navy] spread black smoke where the enemy planes weren’t. Not one hit out of a thousand shots. The Naval Air Group has taken to its heels.
15 June—The naval aviators are robbers.... When they ran off to the mountains, they stole Army provisions....
The defenses of Tinian were dictated by the geography of the island. It is encircled by coral cliffs which rise from the coastline and are a part of the limestone plateau underlying the island. These cliffs range in height from 6 to 100 feet; breaks in the cliff line are rare and where they occur are narrow, leaving little beach space for an invasion force. Along the entire coastline of Tinian, only four beaches were worthy of the name.
The largest and most suitable for use by an amphibious force was in front of Tinian Town in Suharon Harbor. It consisted of several wide, sandy strips. The harbor was mediocre but provided in fair weather limited anchorage for a few ships which could load and unload cargo at two piers available at Tinian Town.
From the beginning, Colonel Ogata assumed that this beach would be the first choice of the Americans. Of the roughly 100 guns in fixed positions on the island—ranging from 7.7mm heavy machine guns to 6-inch British naval rifles—nearly a third were assigned to the defense of Tinian Town and its beaches and to the airfield at Gurguan Point, two-and-a-half miles northwest of the town. Within a two-mile radius of the town were the 2d Battalion of the 50th Infantry Regiment, 1,400 men of the 56th Naval Guard Force, a tank company of the 18th Infantry Regiment, and the 1st Battalion, 135th Infantry Regiment, which had been designated as the mobile counterattack force.
Their area of responsibility extended to Laslo Point, the southernmost part of the island and, on the east, to Masalog Point. It was designated the “Southern Sector” in Ogata’s defense plan.
The remainder of the island was divided into northeastern and northwestern sectors. The northeastern sector included the Ushi Point airfields and a potential landing beach 125 yards wide south of Asiga Point on the east coast of the island. In this sector, between 600 and 1,000 navy personnel were stationed around the Ushi Airfields. The 2d Battalion of the 50th Infantry Regiment, along with an engineer group, was stationed inland of Asagi Point. The northwestern sector contained two narrow strips of beach 1,000 yards apart. One of them was 60 yards wide and the other about 160. They were popular with Japanese civilians. The sand was white and the water was swimmable. They were known locally as the White Beaches and that is what they were called when they were chosen—to the great surprise of the Japanese—as the American invasion route.
This sector was defended very modestly by a single company of infantry, an antitank squad, and, about 500 yards northeast of the White Beaches, gun crews situated in emplacements containing one 37mm antitank gun, one 47mm antitank gun, and two 7.7mm machine guns.
Ogata established his command post in a cave on Mount Lasso in the center of the northern region, roughly equidistant—a little over two miles—from beaches on either side of the island.
He issued on 25 June an operation order saying “the enemy on Saipan can be expected to be planning a landing on Tinian. The area of that landing is estimated to be either Tinian Harbor or Asiga Harbor [on the northeast coast].” Three days later he followed up with a “Defense Force Battle Plan” which outlined only two contingencies:
(A) In the event the enemy lands at Tinian Harbor.
(B) In the event the enemy lands at Asiga Bay.