The Audi A3 is one of several models that VW will produce in its latest brand-new factory in China. The Audi brand is the leader of China's huge -- and hugely profitable -- luxury-car market, where GM's Cadillac is so far just a bit player. Photo credit: Audi

China has been an immense success story for General Motors (GM 0.95%). For the last several years, GM has held the number one market position in the world's biggest auto market -- a position that adds billions to GM's bottom line every year.

GM is still doing well in China, but its market-leading position is under threat. That's because Volkswagen (VWAGY 0.92%), the longtime second-place player in China, is out to take the lead -- and it's spending billions to make that happen.

Volkswagen's latest move is a big push into southern China, a region where Japanese brands like Toyota (TM 0.54%) and Honda (HMC 0.54%) have been strong -- but VW thinks it can be stronger. In this video, Motley Fool contributor John Rosevear looks at VW's latest moves to gain ground in China -- and at why this move could mean trouble for GM in this huge and important market.