Thanks for your post.
The views of attackers appear to follow, generally, what Marten explains.
The points from you post as to Montbrun apply.
Consider what Cockburn said to the Americans (using James, Willaim. The naval history of Great Britain. 1837, volume 6, page 227):
"The rear-admiral's system, and which he had taken care to impart to all the Americans captured by, or voluntarily coming on board, the squadron, was to land without offering molestation to the unopposing inhabitants, either in their persons or properties ; to capture or destroy all articles of merchandise and munitions of war; to be allowed to take off", upon paying the full market price, all such cattle and supplies as the British squadron might require; but, should resistance be offered, or menaces held out, to consider the town as a fortified post, and the male inhabitants as soldiers; the one to be destroyed, the other, with their cattle and stock, to be captured."
To repeat the key phrase, "should resisance be offered, or menaces held out, to consider the town as a fortified post, and the male inhabitants as soldiers, the one to be destroyed, the other, with their cattle and stock, to be captured."
So, the "basics" were the same by the British in American as the French in Portugal. The actual execution and excesses, if any, are a different manner.
So, for the British (as explained in Marten), would not molest the inhabitants if they stayed quitely at home (the following comment from page 228):
"Many of the inhabitants who had remained peaceably in their houses, as a proof that they were well informed of the principle upon which Sir George Cockburn acted, frequently exclaimed to him: " Ah, sir, I told them what would be the consequence of their conduct. It is a great pity so many should suffer for a headstrong few. Those who were the most determined to fire upon you the other day, saying it was impossible you could take the place, were now the first to run away." Several of the houses that were not burnt did, in truth, belong to the chief agents in those violent measures which had caused .such severity on the part of the British; and the very townspeople themselves pointed out the houses."
Thus, the American houses burnt should be limited to those "headstrong few" and American townspeople pointed out the houses of those who acted against the British.
This was not the Portuguese manner of keeping things in order, understandably after each successive invasion.
Thanks for the information. - R