Final answer:
The Crimean War destroyed the Concert of Europe by breaking the alliance between Russia and Austria and shifting the focus of the great powers towards competition. It also revealed the weaknesses of Russia and the need for drastic changes in the country.
Step-by-step explanation:
The Crimean War, which took place from 1854-1856, had a significant impact on the Concert of Europe. The war broke the alliance between Russia and Austria, as Austria chose to stay neutral. This rupture in the alliance resulted in the undoing of the Congress System established at the Congress of Vienna, which was aimed at maintaining a balance of power in Europe.
Furthermore, the war revealed the weaknesses of Russia and its antiquated military and lack of infrastructure. This led to the belief that drastic changes were needed in the country. The war also shifted the focus of the great powers of Europe towards open competition with each other rather than maintaining the collective consensus of the Concert of Europe.