Is your professor American?

Much of what I wrote over on this post is applicable here. https://www.reddit.com/r/AskHistorians/comments/5pi60l/was_field_marshal_montgomerys_meticulous_planning/

There are likely few serious students of military history who would say that Montgomery was the best general the British had in WW2. (Slim usually gets the nod). However, he was successful, there is no denying it.

Unfortunately, he had a significant ego problem, and managed to piss off the Americans in spades. The end result is that one would find very few Americans of the time who would say much good about the man. British folks at the time said much good about him.

The other minor issue is that many of the things Monty did well generally only affected the British, not the Americans. His first WW2 success was in conducting a fighting withdrawl with his portion of the British Expeditionary Force in 1940. The US wasn't even in the war, and all they saw was "British forced out of France." Any nuances are completely missed.

Then there was the success at El Alamein, where he made his reputation with the British forces. Again, pretty much no Americans around to bear witness.

Americans often consider him to have been overly cautious. Given, however, the fact that UK manpower was, well, running a bit thin, this does not strike me as being an unreasonable position. No significant blunders happened as a result in Sicily or Italy after having dealt with the Axis in North Africa.

Monty was the chief planner of the land portion of D-Day in France, which generally worked well enough. The European Theater is where he is often considered to have made three significant blunders.

Firstly, Goodwood: A tank-heavy attack into the teeth of German anti-tank defenses, with obvious results. In Monty's defense, he didn't really have much of a choice. He had no infantry to throw in, (see aforementioned resources and caution), and he had to make a large attack in order to reduce the opposition to the Americans and allow them to break out.

Then there was Market-Garden, the Arnhem assault. This could be considered an unforced error, or it could be considered a gamble worth trying which just didn't pay off. Not many generals had a career without a single setback.

The third was political. In the Battle of the Bulge, he was given command of a bunch of US forces, and generally did quite well with them. The problem was that he gave a press conference at the end, where his verbiage could have perhaps have been better chosen, and it was interpreted as his claiming to have saved the Americans. It wasn't what he was trying for, but it was another definite unforced error.

A fourth cause of irritation for the Americans was his persistent badgering to be placed in overall command of land forces. This was actually not an unreasonable proposal: The command structure of the time was that Eisenhower commanded two Army Groups, in addition to air and sea forces. If the campaign were refought under today's structure, there would, indeed, be a CLFCC (Coalition Forces Land Component Commander) in between the CFC (Coalition Forces Commander) and the operational units. Of course, Monty really wanted to see himself in the position, but the idea of creating the position was not wrong, and given that Supreme Allied Commander was American, the Air and Naval commanders were both British, why would not the Land commander be British as well?

Anyway, Monty got back into form, crossed the Rhine, and generally did well enough for the rest of the war.