A wonderful movie from a historical perspective. Not all old movies could be called classics from the plotline/dramatic perspective. The Leathernecks Have Landed will never be considered a classic.
What it is; - is a record of attitudes and viewpoints of America between the World Wars of the last century. It shows to that time period's sensibilities and the colonial arrogance of gunboat diplomacy as European and outside powers dominated the remnants of the ancient Chinese Empire.
It displays somewhat ambivalently without judgement to the contest between the old order, the Kuomintang, the Chinese Communists with the interference from the outside nations. It shows the culture of the seaport Shanghai.
It is worth seeing this movie as a record of what the American world view was in 1936. Sometimes a movie like this reminds us to the full measure of just how far politically we have come in this modern world, and to those moments that we have not.