For Haig:
Terraine, Gervase Phillips, John Buchanan, Duff Cooper, Ian Malcolm Brown are all pro-Haig historians. They mostly attribute his failings to his background and overall reckon he did a decent job. Some quotes:
patience, sobriety, balance of temper and unshakeable fortitude (Historian: John Buchan) - He believed that Haig's military upbringing gave him these useful and necessary virtues that Haig used well in the face of war.
presided over the integration of entirely new weapons technologies, chemical, aerial and armoured, into the BEF's tactical system (Historian: Gervase Phillips) - Attibuted the success of the final 1918 campaign to Haig [not Foch] for finally bringing together and integrating new tactics and technologies.
impose an inflexible procedure as compensation for lack of training (Historian: John Terraine) - Terraine says [along with other things] that Haig found it necessary to use an inflexible training procedure because this was the only possible way they could train the conscripted men upto battlefield standards.
Duff Cooper (Official British War Historian) explains that to have refused to fight then and there would have meant the abandonment of Verdun to its fate and the breakdown of the co-operation with the French... - Reasons for why the Battle of the Somme was brought forward from August to July.
Ian Malcolm Brown praised Haig for his excellent administrative and transport systems.
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Personally, I thought Haig was an utter douche, however, I wrote a very polemic essay that was pro-Haig simply to piss my teacher off because it seemed like a good idea at the time
It wasn't an assessment task anyway.
Finding anti-Haig and anti-British General historians is very easy, such as, Denis Winter and John Laffin.