The Maasai  Kenya's most famous tribe were the most powerful tribe in Kenya. Their  territory reached its largest size in the mid-19th century, and covered almost all of the Great Rift Valley and adjacent lands from Mount Marsabit in the north to Dodoma in the south.[13] At this time the Maasai, as well as the larger Nilotic group they were part of, raised cattle as far east as the Tanga coast in Tanganyika (now mainland Tanzania). Raiders used spears and shields, but were most feared for throwing clubs (orinka) which could be accurately thrown from up to 70 paces (appx. 100 metres). In 1852, there was a report of a concentration of 800 Maasai warriors on the move in what is now Kenya. In 1857, after having depopulated the "Wakuafi wilderness" in what is now southeastern Kenya, Maasai warriors threatened Mombasa on the Kenyan coast.

The Maasai people stood against slavery and lived alongside most wild animals with an aversion to eating game and birds. Maasai land now has East Africa's finest game areas. Maasai society never condoned traffic of human beings, and outsiders looking for people to enslave avoided the Maasai.

Lenana wanted the British to help the Maasai to be powerful once more, so that they could defeat the Nandi who were their big enemy at the time.

He also wanted support to fight his brother, Sendeyo, who wanted to become the leader.

This is why around 1905-1906, Lenana sent 1 000 Maasai warriors to fight other communities for the British and also allowed the British to construct a railway line through his territory.

Later, the British turned against the Maasai and wanted part of their land for white settlers.

Lenana was made to sign an agreement with the British that moved all the Maasai from their land and sent them to live in two main reserves, one around Ngong in Kajiado and another in Laikipia.

In 1911, more settlers arrived and more land was needed.

A second agreement was signed, and the Maasai under Lenana were forced to move again, from Laikipia to the Ngong reserve.