Answer:
1. Qing Dynasty was in decline after the effects of the Opium Wars which led to instability within the empire. The dynasty lost possessions in Korea and East Asia therefore increasing the tension. The Ottoman empire also began to yield to the pressure of the more advanced Western nations whilst lost territories in Moldova and Greece. This caused the empire to weaken the Ottoman and lost influence.
2. The Crimean War was caused for the Russian expansionism and the fear of the Ottoman Empire to disappear. Warfare changed due to the abolition of the Letter of marque, which allowed mercenaries to act under the command of national military companies.
3. Russia lost nearly half of million troops and also lost terrotories in the Danubian Principalities.
4. During the second half of XIX century, China was weaken due to the aftermath of the Opium Wars and the following treaties which expanded the influence of Western nations. A big part of the population was unhappy with the Qing Dynasty and wanted a change of government. The Taiping Rebellion led to several revolts and conflicts which caused the fall of the Empire in 1911.
Step-by-step explanation: