You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

what is the first event mentioned?, Context: The Russian Revolution is the series of revolutions in Russia in 1917, which destroyed the Tsarist autocracy and led to the creation of the Soviet Union. Following the abdication of Nicholas II of Russia, the Russian Provisional Government was established. In October 1917, a red faction revolution occurred in which the Red Guard, armed groups of workers and deserting soldiers directed by the Bolshevik Party, seized control of Saint Petersburg (then known as Petrograd) and began an immediate armed takeover of cities and villages throughout the former Russian Empire.
Solution: Russian Revolution
Why? This is a good example, and the Russian Revolution is the first event mentioned.

New input: What did the battles of Brentford and Turnham Green lead to?, Context: During the English Civil War the majority of Londoners supported the Parliamentary cause. After an initial advance by the Royalists in 1642 culminating in the battles of Brentford and Turnham Green, London was surrounded by defensive perimeter wall known as the Lines of Communication. The lines were built by an up to 20,000 people, and were completed in under two months. The fortifications failed their only test when the New Model Army entered London in 1647, and they were levelled by Parliament the same year.
Solution:
London was surrounded by defensive perimeter wall known as the Lines of Communication