This is going to require the knowledge of someone who has more inside knowledge of the production of classic TVB series than I do.
The opening titles of LOCH '82 feature some very impressive scenes of Mongolian cavalry and infantrymen on the grassy steppes. There might not have been vast numbers of people and horses, but the attempt to create the illusion of vast numbers succeeded. Moreover, the costumes worn by these ersatz Mongolian warriors looked very authentic...much more authentic than the studio costumes that TVB used for "Mongolian" soldiers in the actual series episodes themselves.
During 1982/1983, the People's Republic of China was not yet as open to foreign film/television production crews using its territory for filming as it is today. The PRC was more restrictive at that time than it is now about filming within its borders. In 1982/1983, it would have been unfeasible for TVB to do extensive shooting within mainland China.
Moreover, the sheer number of men and horses (not the thousands meant to be depicted, but still...dozens) looked prohibitively costly for a 1982/1983 period TVB production, and the costumes worn by the extras did *not* resemble standard TVB ancient production costumes (too authentic-looking, especially for the 1980s when telegenic considerations outweighed historical accuracy) of the period. Finally, there are no wide, flat, grassy plains anywhere near Hong Kong in 1982/1983 that such scenes could have been filmed upon.
So where did TVB get the footage for the opening titles of LOCH '82, Part 1? Did they really blow the budget (i.e. more than they spent on the actual episodes) to simulate a realistic 13th Century Mongolian cavalry charge within China's borders (or the actual Mongolia, which would have been less politically restrictive, but even more logistically prohibitive in terms of cost of transporting personnel and equipment to the site)? Or was this stock footage taken from some cultural event held in Mongolia during the early 1980s?