“The Manhattan Project for the US atomic bomb involved thousands of people, who kept it secret. So why then couldn’t a conspiracy involve a large number of people?”

This is not a good example, IMHO. Even at the time, lots of people knew something was going on in New Mexico and elsewhere, and that it involved many physicists (*). Anyone with a good knowledge of atomic physics probably had a good idea of what the goal was. Certainly others, such as Stalin, who were not on official Cc lists, had near perfect knowledge.

And soon after the war, when the need for current secrecy was over, almost the whole story came out.

I do not believe anyone doubts the ability to keep even big projects out of general knowledge for a time (the breaking of the WW-II German and Japanese codes is a better example, where the targets it seems really had no idea). I think the question involves keeping it secret for years after secrecy serves no apparent purpose. Ted’s example has such a secret kept for over 60 years.

• In WW-II, a Princeton physicist gets a letter from a colleague in New Mexico saying “something you would like to work on is going on and you should come. I cannot say more, but be in Albuquerque on this train on this day…” Guy goes to buy a ticket at Princeton Station. The station master says “I would not do that” “Why not?” “You are a physicist, right? Well, 15 physicists have gone to Albuquerque in the last year and NOT ONE HAS COME BACK!”

You have to be very careful about that evidence though, for two reasons. First, it’s talkin mostly about the 1914-early 1915 period when the Gallipoli plan was being developed and when Kitchener’s word was being treated seriously. That changed dramatically after the Shells Scandal of May 1915 and the rearrangement of the government by Asquith. Kitchener’s authority continued to slip throughout 1915, most notably when Lord Derby (the “uncrowned King of the North”) was brought south to restart flagging recruiting efforts. By the end of 1915, Kitchener’s power was a shadow of its former self.

Second, remember that everyone at that meeting it trying to escape blame, and who better to put it on than the dead guy? The naval testimony is particularly sketchy: Admiral Jackie Fisher, who was First Sea Lord at that point, had never remained silent about anything in his life, and it is unlikely that he had started then.

The Parliamentary Enquiry into Gallipoli contains some interesting comments about Kitchener. According to the evidence given, K’s advice on army matters was accepted without question at the top level (the Cabinet, from memory). The naval advisors kept quiet when Winnie was proposing his plans, although they later claimed to disagree.
But you have to remember that this enquiry succeeded in getting Winnie fired – probably its main purpose.

DSW

The modern way around that, of course, is not to rely on keeping things secret for long. Just pump out BS and lies, and discredit anybody who speaks the truth. One’s followers will have lots of motive to deny the truth, and to pump out lies and BS themeselves.

Plus there is always a huge double-standard: to admit a conspiracy by people we sympathize with we require undeniable proof (that almost never exists), yet when it comes to conspiracies carried out by people we don’t like – any kind of evidence (or even a gut feeling) is good enough.

Given that the British had a bad record of underestimating German minelaying and that the naval staff was probably a bit distracted by the Battle of Jutland (fought only a few days earlier), simple mistakes are an adequate explanation.

You’re not at all wrong. But in this narrative, which is all about the Middle East, Gallipoli and the Ottoman front play a primary role.

I am saying that I’m stunned that the Admiralty managed to screw up this badly and keep it completely quiet until long after all involved were dead. I’m especially stunned because Naval Intelligence got it right, and I would have thought that someone there might have leaked. The knowledge that you were right but got blamed anyway is a powerful motivator for most people.

2. Kitchener’s influence on strategy was actually quite positive. He was not the one who had committed the British to France. The General Staff had done so before the war, while Kitchener was in Egypt. Kitchener was the only one to recognize that Britain was going to need a large army to fight this war and set about recruiting it from the very start. His control over the actual fighting in the field was fairly small—it was Sir John French and Haig who had the main influence on that. The one exception to this might be the Gallipoli debacle.