1. Trade imbalance with Great Britain, which led to Opium imports into China, which the Chinese tried to ban but failed. This led to the Opium Wars.
2. An outcome of the Opium wars was British victory leading to the Chinese signing unequal treaties, opening trade, giving land to the British and forcing the Chinese to pay for the war.
3. The Europeans established 'spheres of influence' in certain territories of China, leading to the Chinese fighting back, to gain independence.