The statement refers to an event where both Mohammedans (Muslims) and Hindus were united and hence, the division tactic couldn`t be applied by the British rule.

Option 1: The Revolt of 1857 was a rebellion against British rule by the soldiers (sepoys) but it was not notably spread among Hindu and Muslim civilians.

Option 2: The Champaran Satyagraha in 1917 was mainly a peasant movement led by Mahatma Gandhi against indigo planters, not specifically uniting Hindus and Muslims against colonial rule.

Option 3: The Khilafat and Non-Cooperation Movement (1919-22) is the correct answer. This was a significant instance when both Hindu and Muslim communities united under a single political action against British rule. It was in response to the unjust actions taken against the Ottoman Caliph, a figure of significance to Muslims, and also in the broader context of seeking Independence.

Option 4: The August Movement of 1942, also known as the Quit India movement, again, was not specifically a Hindu-Muslim united front.

Therefore, considering these points, it makes the statement of Aitchison applicable to Option 3.