12/6/41 17:00 hours – Just south of Pearl

The Japanese fleet class submarine I-6 was one of twelve positioned outside Pearl to support the raid. She and four others were each carrying a midget sub which was to enter the harbor and inflict damage on ships which attempted to escape. Serving on these midgets was essentially a one way trip, their crews would either be killed or captured, they had no way to return to the mother sub. They lacked the range to return and a means to find the mother sub. She could not afford to wait for them, this would expose her to unacceptable risks. The larger subs were to maintain a watch from offshore and follow any large ship movements — but they must remain out of sight until 8:00 AM Pearl time the next day. After the air attack began they could pick off any ships that were able to get under way and leave the harbor. Most of the submarine crew members considered their mission to the very mouth of the American Fleet headquarters suicidal. Few expected to return to Japan. Most had posted final letters to their families with locks of hair before leaving the homeland.

Just after 1730 the watch on the I-6 picked up the sounds of heavy ships moving out of the harbor. The captain took his boat to periscope depth and observed battleships, cruisers and destroyers moving out to sea. He counted seven battleships, three cruisers and at least eight destroyers. He waited until 1800 and sent off a short signal to Fleet Headquarters informing them of the movement. This done, he dived and launched the midget sub he carried. The midget would have to leave for the beach early and bide its time till the following morning, the I-6 could wait no longer. It must take station and follow the fleet. It must be in position to attack in the morning.

All of the submarines except the two stationed to the south west heard the fleet movement and were following. Like the I-6, the others carrying the midgets cast them off early and followed the fleet. The two remaining submarines would continue to monitor their assigned areas.

12/6/41 1800 hours – Pearl

The Pennsylvania finally cleared dry dock and with three destroyers left the harbor as planned. By now they were some forty miles behind the main body of the fleet but would join it during the night. The I-6 had just begun to shadow the battleship fleet, running at high speed on the surface when a large ship was sighted dead astern on the same course and closing very fast. If they did not get out of its way they would be overrun. The sub turned to port, dived and waited. The ship passed the submerged I-6 with its three escorts. When the I-6 came to periscope depth it identified the ship as the Pennsylvania, the flagship of the Pacific battleship fleet, a real prize. He considered attacking her but the orders were explicit, there was to be no attack till after 8:00 on Sunday morning. He noted the ship, she was steaming at about twenty seven knots. Clearly, she was in a hurry. After she passed a second message was sent to Fleet Headquarters with this information. The I-6 followed at about sixteen knots even though the much faster Pennsylvania quickly pulled away. The captain knew approximately where she was headed and that soon she would slow and the I-6 could slip into a position for the attack her captain knew would come. He would patiently prepare and wait for the signal. He was certain he knew her destination and her intent. His torpedo tubes were loaded and ready.