ESTJ seems good for Montgomery, I'd go with it. He was famed for winning battles with his meticulous advance planning, and an operational rigidity once in battle which often obstructed his own side's progress. He was also a stickler for efficiency, notably outspoken, rigid in his opinions; and so lacking in political tact (Te on overdrive?) that he was often in conflict with his colleagues, and the government went to some trouble to keep his divisive personal views from becoming public, mounting what amounted to a gagging operation against him while he was in high office.
YLJ, that post was unbelievable! I don't doubt there are a lot of -NTJ generals, but you seem to have decided almost every famous military commander in history must be one on the basis that NTJs tend to make good ones, and that since they are good they must therefore be NTJs, rather than looking at specific personal traits in each case.
To take one example, the person in your avatar, Murat, strikes me as a classic example of an ES_P. I would personally go with ESFP. He wasn't any kind of strategic planner, but a dashing, impetuous cavalry commander, extremely popular with his men, most notable for charging into battle, often with reckless abandon, and carrying all before him due to his vigorous, inspirational command, personal courage, and ability to quickly adapt to the needs of the moment. Murat's swiftness, courage, and unpredictability provided the perfect foil for Napoleon's grand strategic thinking. (Napoleon was probably indeed an -NTJ, I'm not so sure about the E bit though) He wasn't a sucessful grand commander himself when having to organise mixed forces, I don't believe he won a significant battle in his own right as king of Naples, and was decisively defeated at Tolentino by a weaker Austrian force.