When did the closed-door policy of the Qing Dynasty begin, which left China behind for nearly 300 years?

Since the Qing dynasty entered the customs, it has pursued a closed-door policy, which has almost become the "constitutional order" of the whole Qing dynasty. Although the specific requirements are different in different periods, closing the country to the outside world has always been their basic national policy.

At first, the Qing dynasty mainly closed its doors to the outside world, strictly controlled a series of details in border trade and foreign affairs, and prohibited foreign civil and commercial activities. Later, this kind of closure extended to the territorial waters, and even created a wonderful decree that "sails are not allowed to go to sea". Completely ignoring the "huge" imbalance in the proportion of casualties in the jaxa war, rejecting a series of advanced western science and technology, especially advanced weapons and equipment, fearing that these things will make the children of the Eight Banners lose courage. As a result, a person's independent courage "courage" collapsed instantly when he encountered a strong ship and a sharp gun.