How did our submarines escape?

If the submarine was submerged, the most important thing would be to be very quiet so that the Japanese sonar didn’t pick it up. Most often, that also meant moving very slowly.

Once an attack run was started by a Japanese ASW ship, they would approach at high speed. The ASW ships also had to get clear of the depth charge explosion. When they are running at high speed their sonar would be overwhelmed by their own ship noises and the flow of water over their equipment. That allowed the submarine captain a brief opportunity for evasion tactics such as turning, changing speed or changing depth.However, if there were multiple ships attacking the submarine, the other escorts could move slowly enough for their sonars to still be effective.

Generally, it was a cat and mouse game. It would be the wits and ingenuity of the submarine captain against his attacker(s).The submarine also had the advantage of using all three dimensions. The attackers had to estimate not just where the submarine was but also how deep it was. Depth charges had to get pretty close, probably within 25 feet or so, to the submarine to breach the hull and sink it.

Captains would also be looking for a “layer.” That was a fairly sudden change in temperature as the boat goes deeper. The change in temperature can distort sonar, bending it to confuse the pulse, or even reflect it allowing the submarine to hide. Such a layer was called a thermocline. There was a bathythermograph in the control room. It was a small box that records the water temperature at various depths.

Our submarines were rather sturdy and could absorb a fair amount of damage. Sometimes the key was to contain and repair the damage long enough so that the Japanese would just assume that they must have been successful. It seems that it was sometimes just a matter of outlasting them.

If the submarine was on the surface, other factors come into play. Of course, one choice was to submerge quickly and then turn or go deep before the attacker comes close. If the enemy vessel was small enough, it might have been possible to outrun it.

Assuming that it was in the hours of less light, there are things that can help make our submarines less visible to an attacker. One tactic was to point towards or away from the enemy to show the smallest profile. Another was to use fog or rain squalls to hide in.

We tried to be less visible to begin with. U. S. submarines experimented with colors to determine what was least visible. Black was too dark. As a result, the vertical surfaces would be painted a shade of dark grey. Horizontal surfaces were black so that they could blend into the depths when submerged. Captains would try to have the enemy ships between themselves and the moon so the boats were less visible during an attack.