Operational Question

[Kirk]

Did WW2 subs run mostly surfaced and dived only on being attacked or about to attack a target or did they run on the surface during the night and dove during the daytime? If they did dived during the day what was their speed? Thanks for any answers.

[A Very Super Market]

Hm... in early way, you could run surfaced and dive when only when attacked. But when RADAR is developed, the captains learned that they were only marginally safe during the night. Daytime became extremely hazardous as the war progressed and new airbases and new aircradt became operational. Eventually, even surfacing at night became dangerous, aircraft could be completely guided by RADAR.

But thats the Atlantic

The axis powers never had RADAR or anything, so allied subs could operate surfaced a lot. But the Pacific was swarming with planes, and the water is fairly clear, so the US submarine captains would also dive during the day, but only when it was deemed dangerous to be exposed

[Rockin Robbins]

The World War II submarine was a surface ship which could submerge when absolutely necessary and for the absolute minimal amount of time necessary to save their scrawny little necks. The Japanese did have radar, both on surface ships and in planes after spring of 1944.

Still wars are to be fought and subs are to remain on the surface at 9 knots with radar operational at all times to search the greatest number of square miles of ocean surface to find and sink the greatest amount of enemy shipping.

Force the World War II sub down and keep him down and his productivity becomes zero and he dies quickly. The Germans experienced that. We, by not being bound to established procedures an innovating our way out of dilemmas during the war, found ways to spend increasing portions of the cruise on the surface and sinking Japanese shipping.

Let's put it this way. Germans, using highly defective strategy, tactics and equipment, succeeded in sinking a whopping 1% of total convoy tonnage during the war. American submarines, making up strategy as they went and getting more efficient as Japanese anti-sub techniques got better, sank 80% of all Japanese shipping.

When you quit fighting and start hiding you have lost the war. Submarine stealth is intended to be an offensive weapon.

[tater]

US skippers were still afraid of DF wrt their radars as I recall. I think they'd turn the radar on for a while every hour, then turn it off. Later in the war you read of surfaced "high periscope" patrolling, too. Earlier in the war, submerged during daylight was pretty common for fleet boats, though (they had a 2 day endurance submerged at 2 knots or so).

"Keep them down" is indeed the crux of ww2 ASW doctrine done right. The Japanese actually had this notion (read the post-war interviews in the strategic bombing survey), but their execution was less creditable. The Allies not only had and used this doctrine, they also had sigint and code breaking. The sigint alone would have utterly doomed the u-boats. It's not just sinking subs, but simply putting ASW assets where the u-boats are forces them to stay down. Combined with putting the convoys where the hunter killers (and u-boats) are NOT, and you've crippled them.

For all the amazing tonnage sunk by u-boats (11-12 million tons, right?), it was still only a few ships sunk per sub lost (~10,000 tons per boat lost). A merchant ship, banged out in a few days or a week, crewed by at most a couple dozen guys is a good trade (particularly with a good % of the crews rescued) for a far harder to produce sub, and what, ~4 dozen highly trained men?

US subs sank a fraction of the tonnage, <5 million tons, but it was ~100,000 tons per boat lost.