Some of these, such as the Somme, have had their death toll squarely aimed at incompetence among the generals.

As George Pickett might have put it, I would have thought that the enemy might also have had something to do with it.

Firstly, there are any number of personalities who were actually present at the battles you mentioned who would argue that the actions were well-conceived, but poorly executed. For instance, Churchill never intended for the disastrous amphibious landing at the Dardanelles to take place and had planned to force the Narrows by sea, making use of pre-dreadnoughts that would have been target practice for the German High Seas Fleet and use them to clear the way to Constantinople by sea to knock the Ottomans out of the war. However, he underestimated the depth of feeling British Admirals had for their old commands and the shock that the loss of a ship would have: the Royal Navy lost more ships on a single day of trying to force the Narrows than it had at any point since Trafalgar. Vice Admiral Sir John de Robeck panicked at the sight of resistance from the shore, which meant that the battleships held back and the minesweepers had to go in without cover. This despite the fact that Commodore (later Admiral of the Fleet Sir) Roger Keyes, in command of the minesweepers, was all in favour of pushing on on the first day. Keyes was one of the Royal Navy's most senior commanders at the start of the Second World War and supported the Dardanelles plan until he died. So did one Captain Clement Attlee, later Leader of the Labour Party and Deputy Prime Minister to Churchill in the Second World War, who was the second-to-last man to be evacuated from Suvla Bay when the Gallipoli Campaign was closed down (the last was his division's Commanding General). Attlee was convinced that the Gallipoli strategy had been a bold and correct one, which in the words of his biographer, "gave him a lifelong admiration for Churchill as a military strategist which contributed enormously to their working relationship in the Second World War."

Secondly, I would argue that expressing remorse would imply that any of them felt guilt at what they had done and recognised that they had been wrong to do it. To focus on Field Marshal Sir Douglas Haig, he certainly did not, and would never have apologised for his actions. But that certainly did not mean he did not care. Haig wrote in 1917:

"No one can visit the Somme battlefield without being impressed with the magnitude of the effort made by the British Army. For five long months this battle continued. Not one battle, but a series of great battles, were methodically waged by numerous divisions in succession, so that credit for pluck and resolution has been earned by men from every part of the Empire. And credit must be paid, not only to the Private soldier in the ranks, but also to those splendid young officers who commanded platoons, companies and battalions. Although new to this terrible "Game of War" they were able, time and again, to form up their commands in the darkness of the night, and in spite of wire, shell holes, and other obstacles, lead them forward in the grey morning to the attack of these tremendous positions. To many it meant certain death, and all must have known that before they started. Surely it is the knowledge of the great stake at issue, the existence of England as a free nation, that served them for such heroic deeds. I have not the time to put down all the thoughts which rush into my mind when I think of all these fine fellows, who have either given their lives for their country, or have been maimed in its service. Later on I hope we have a Prime Minister and a Government who will do them justice."

The casualties suffered under Haig's command cannot be considered to be excessive in the context of the First World War. Armies larger than ever before were crammed into a confined battlefield and so had the strength to hold the entire line. This time there were no flanks to turn or indirect approaches to take. Every attack would have to be a frontal one. This was the true cause of the carnage of the Great War: not incompetent Generals, the mere disparity between manoeuvre and firepower. The destructive power available to the armies of the Great War was immense, but only from fixed positions. It would not be until 1917 and 1918 that mobile firepower in the form of tanks, creeping barrages, and man-portable machine guns became available. During the Battle of the Frontiers from 6 August to 5 September 1914, the French took 329,000 casualties. At Verdun they took 336,000 casualties. During the Spring Offensive of 1918 the Germans took 688,341 casualties. However, I have yet to see references to "Butcher Joffre", "Butcher Petain", or "Butcher Ludendorff". Why should Haig be considered uniquely guilty and in need of showing remorse?

But he did care. Early in his command of the BEF Haig visited a number of Casualty Clearing Stations. He was so deeply affected by the experience that he was advised to never go again for the sake of his mental health. While sitting for his official portrait, he suddenly burst out to the painter; “Why waste your time painting me? Go and paint the men. They’re the fellows that are out saving the world, and they’re getting killed every day.” The trenches were horrible places to live and Haig knew it: the British Army rotated men in and out continuously. Between battles, a battalion spent on average 10 days a month in the trench system and of those, rarely more than three days right up on the front line. It was not unusual to be out of the line for a month. While iron rations of bully beef and biscuits were monotonous, behind the lines in reserve and rest areas, fresh food was abundant, with a daily ration of meat, a rare luxury indeed for civilians at home. The standard ration never dropped below 4,100 calories, and most men found they gained weight while in the Army. The attention paid to welfare in the BEF under Haig's command meant that the British Army was the only army on the Western Front not to suffer a serious collapse in morale or a general outbreak of indiscipline, as nearly destroyed the French Army and brought the German Army to its knees.

It cannot be said that Haig was loved by his men, as might (extremely arguably) be said of Montgomery. Nor would any soldier passionately declare that they would rather see him in a fight than a reinforcement of ten thousand men any day, as a Redcoat once said of Wellington. Nevertheless, he was respected, and in turn respected his men. His valet, Sergeant Secrett, remarked that Haig, notably inarticulate even among his own class, "managed to convey to Tommy the fact that he respected him." He was not loved, for "he was too remote – but that was not his fault. The show was too big."

After the war, Haig worked to create the country he had hoped to see when he wrote in 1917. He refused all honours until appropriate provision was made for veterans. In July 1919 he delivered an infuriated denouncement of the government's Armed Forces pensions policy to a parliamentary committee, which was embarrassing enough for the government to change tack. He was an instrumental figure in the coordination of various disparate veterans' groups and the eventual foundation of the British Legion in June 1921. It is Douglas Haig we have to thank for the Remembrance Poppy, which until recently did not have inscribed on it “Poppy Appeal”, but “Haig Fund”. He was observed to work long into the night personally answering correspondence from his old soldiers. In the opinion of Colonel Mickey Ryan, his old chief medical officer, he worked himself to death. He made highly-publicised tours of Canada and South Africa to raise similar support for veterans. In 1927, appalled by how Irish veterans in the now-independent Irish Free State were forgotten as embarrassments to the Republican cause, he made an emotional appeal to Britain to remember the sacrifice of Irish Catholics. Alas it fell on deaf ears, and he publicly regretted the poor response. He was a regular guest of honour at the unveiling of war memorials, where despite the emotionally-charged atmosphere, there is no evidence of any opprobrium being directed at Haig.

What I want to have got across here is that while Haig certainly didn't think he had anything to apologise for, this did not mean he was in anyway uncaring. And what is more, both his soldiers and the British people seem to have thought so: when he died unexpectedly of a heart attack on January 29th 1928 at the age of 66, more people turned out for his state funeral than would later do for Princess Diana.

Sources:

Gordon Corrigan, Mud, Blood and Poppycock

John Keegan, The First World War

Andrew Roberts, Churchill: Walking With Destiny

Peter Simkins, et al., The First World War: The War to End All Wars

Gary Sheffield, The Chief: Douglas Haig and the British Army

Matthias Strohn, et al., 1918: Winning the War, Losing the War