Perhaps the largest amounts of intentional and unintentional (captured) military surplus happened during King George's War and the FIW.
The French Fortress Louisbourg was one of the most extensive and expensive European Forts when it was finished in 1740. It sat off the Nova Scotia shore just a wee bit on Cape Breton island. Actually the distance to land was sort of on the order of a wide moat. It served two main purposes, 1. To protect the French Fishing and Sealing Industry and 2. It was the main storage Arsenal for French Military (French Marines/Regulars and their Militia) and Gift Arms for Native American trade for all of Canada.
What is so surprising was it had two main weaknesses. The first was it was so far from Montreal or Quebec, that if it got attacked, reinforcements were much too far away to do them any good. The second and worst weakness was though it had excellent defense and offensive capabilities from the Sea side, they did not design any real defensive crenelations in the rear to defend against land attack.
During King George's War (the North American part of the War of the Austrian Succession) New Englanders were extremely keen to take the fortress because of competition in the fishing and Sealing Industries, plus French Ships from there sometimes threatened British American commercial ships. With the exception of a small number of some British War and Supply Ships, this was the first All American good sized Amphibious Operation. (Some Americans held temporary British Officer Commissions and that's why sometimes historians mention some "British Officers," though that's a mistake thinking they were British.) They came in the landward side of the island, drug some field guns onto the hills behind the forts and banged away with NO French Cannon fire to contend with. They took the Fortress, emptied all the arms out of it (which probably was a large number, but it seems they didn't record how many) and probably took them back for distribution to the Colonies from whence the troops came and may have burned the fortress. However, since it was largely made of stone, burning wasn't going to destroy the Fortress in a major way.
Fortress Louisbourg was given BACK to the French at the end of the War of the Austrian Succession in trade for some border towns in what is now Belgium. France repaired the fortress and filled it back up with relatively new made weapons as much or more than had been stored there the first time. Then the Fortress was once again the bane of the British American Fishing and Sealing Industries. I imagine that wasn't real popular with New Englanders even though they got a major amount of "free, surplus" trade and military arms and equipment from taking it.
Not long after the French got Fortress Louisbourg back up to snuff and restocked, the French and Indian War broke out in North America in 1756, as part of the global Seven Years War. This was a much more serious war with greater numbers of troops on both sides than King George's War had been, as both sides recognized the winner of this War would take over Canada. However, when Braddock got defeated and his forces almost massacred, it put British America in a real pickle.
Governor Shirley of Massachusetts having been a British Officer, was chosen as the Commander in Chief of British forces in North America to replace Braddock. He was expected to raise at least two Regular Regiments here and that included arming and equipping them, along with all the Militia forces called upon for campaigns in North America. This was a Herculean task by itself, especially as there were so few muskets and military equipment in Colonial Armories. He called on British Ordnance to supply him with 50,000 stands of Arms, as the minimum to meet the requirements for both offense and defense, but there was a huge problem with his request.
British Ordnance didn't have quite that many stands of arms in total and they were expected to arm all British Forces on the home islands, the additional new forces for British Regiments that were to fight on the continent and other places worldwide - including North America. SHEESH. British Ordnance did the best they could, but America was a fairly low priority in that war, at least at first. So British Ordnance sent 10,000 stands of Arms........... the first major surplus arms quantity given to the North American Colonies. However, those stands of arms arrived here in really poor shape.
Many complaints were recorded of the Arms arriving here in extremely rusty shape, the locks wouldn't work or spark, bayonets would not fit, holes in the Cartouche Boxes were too small to hold Cartouches (Paper Cartridges) etc., etc. Many of the Muskets had come from emergency purchases by the Ordnance Department during the first years of King George's War and they were NOT up to British Military Standards even then, but that's the best that could be purchased at the time. Well, now it was 12-14 years later and beyond the normal service life of British Muskets at the time of only 10-12 years. YIKES!
Gotta give Governor Shirley credit though, he had done a lot of work organizing the first attack on Fortress Louisbourg in 1745 and may or even probably began the same thing in the FIW until he was recalled in 1757. OK, there was a DIRE need of military arms and accoutrements and they were not coming from England, except for the numbers of paramilitary arms the individual colonies could afford to buy from the Civilian Gun Trade. So no matter if it was initiated by Governor Shirley or not, a second amphibious assault was sent against Fortress Louisbourg in 1758.
(As I write this, I'm reminded of and wonder if the British/British American Forces sang something similar to the WWII song of "We did it before and we can do it again........on their way to the Fortress?" LOL)_
Believe it or not, the combined British/British American Forces used the same basic battle plan used before in 1745. They must have been astounded the French had done virtually nothing new to protect and defend the rear of the Fortress!!! History does record they were astounded to find around 15,000 stands of arms and these would have been much newer models than had been there in 1745. In one fell swoop, they had captured 50 percent more of better quality arms and accoutrements than British Ordnance had sent. Talk about a period Blue Light Special!!!
Unlike what happened in 1745, we know more about the disposition of the French Arms captured there in 1758. First, it seems that this time, every soldier who wanted one, got a complete stand of arms for himself clear and free. We know that British Regular Light Infantry troops took to the French Muskets over the British Light Infantry Carbines issued to them as they found the French Muskets "more robust than the British Carbines." They emptied out the rest of the arms and divvied them up to active forces and to the northern colonies. So this was the second major unintentional/captured surplus arms quantity in North America in the 18th century.
Some of those arms were used by Patriot Forces at least in the early part of the American Revolution.
Gus