Lord Haig did not send 'millions' to their deaths. Total British Empire deaths, covering all campaigns and including those in which Haig was not involved, totalled 908,000. The 10 million with no known grave mentioned by Professor Carter is clearly ludicrous given the fact that Britain mobilised just over eight million men in the course of the war.
Appalling though the figures are, British casualty rates were, if anything, less than those of other major combatants. As a general, Haig was no better or worse than the majority of his contemporaries, and it is by those standards that he should be judged.