The Supreme Court decision to nullify Kenya's presidential election and hold a new poll has reignited fears that the country could descend into violence.

Kenya certainly has an extensive track record of political violence. This has generally been ethnically mobilised, stemming from grievances over land and exacerbated by vigilantes and militias deployed by politicians to garner support.

Ethnic land grievances can be traced back to colonial rule. White settlers expropriated vast tracts of land, particularly in the fertile Rift Valley which was traditionally a Kalenjin and Maasai area. The creation of ethnically exclusive reserves and African labour forces saw further tribal displacement.

Discriminatory land policies were abolished after the Mau Mau militia (also known as the Land Freedom Army) uprising. But land was not returned to its traditional owners.

After independence, land redistribution under Kenya's first president Jomo Kenyatta saw his Kikuyu tribe favoured. Civil service appointments also saw preferential treatment of the Kikuyu, and the only opposition party was banned. This trend continued under Kenyatta's successor Daniel Moi. He favoured his Kalenjin tribe and formalised one-party rule via constitutional amendment.

State-sponsored vigilantes and militias

In due course, pressure mounted for the amendment to be abolished. This reached its peak in early 1991 when foreign aid to Kenya was withheld, and Jaramogi Oginga Odinga of the Luo tribe announced the reestablishment of an opposition party.

Moi's party, the Kenya Africa National Union (KANU), feared the loss of political power. In September 1991, it began to push for the devolution of power under traditional ownership with a focus on the Rift Valley.

By the end of October, this had triggered a wave of ethnic violence. Self-proclaimed 'Kalenjin Warriors' warned the Luo and other non-Kalenjin to leave the Rift Valley or face the consequences. This escalated into retaliatory and counter-retaliatory attacks, leaving approximately 1,500 dead and 300,000 displaced.

A parliamentary report found that the 'Kalenjin Warriors' militia was supported and funded by KANU officials. The Kikuyu were particularly persecuted, providing recruits for the Mungiki vigilante group who saw themselves as modern Mau Mau.

President Moi eventually repealed one-party rule and went on to win the 1992 election. Human rights groups have speculated that his win was due to the large number of Kenyans who were displaced by the Rift Valley attacks and thus unable to vote. Despite Moi's win, the violence lingered well into 1994.

Unleashing terror

Preceding the 1997 election, KANU raised the devolution agenda again. This time it focused on Kenya's Coastal Province. The indigenous Digo community were mobilised against tribes from central and western Kenya. Up to 10,000 people were displaced and 104 were killed.

A judicial report found that KANU officials recruited and funded the militia 'Digo Raiders'. Again, the displacement of voters was beneficial to KANU.

In Nairobi, an opposition stronghold, voters faced intimidation from Jeshi la Mzee, a vigilante group allegedly funded by a KANU minister. The post-election period also saw a resurgence of conflict between the Kalenjin and Kikuyu in Rift Valley.

Prior to the 2002 election, Jeshi la Mzee resumed attacks on KANU opponents. Conflict between Mungiki, now linked to KANU successor Uhuru Kenyatta, and the Taliban, linked to Luo opposition leaders, led to 18 vigilante groups being outlawed.

A short lived peace ensued as Kenyans came together to elect a non-KANU leader for the first time in the country's history. This was President Mwai Kibaki, a Kikuyu and leader of the newly formed National Rainbow Coalition (NARC), a multi-ethnic alliance.

Trouble returns

Peace within the new alliance did not last long. The Kikuyu elite, termed the Mount Kenya Mafia, monopolised power once again. During the 2005 referendum campaigns, NARC was split along ethnic lines, with the Kikuyu endorsing the yes vote and Luo endorsing the no vote. The Luo subsequently broke away and formed the Orange Democratic Movement under Raila Odinga.

Tension intensified with the 2007 re-election of Kibaki, contested by Odinga. Ethnic violence broke out again, chiefly in the Rift Valley. The Kalenjin Warriors and Mungiki were heavily involved. Around 1,300 people were killed and 650,000 displaced.

The conflict only deescalated after an agreement was signed placing Odinga as Prime Minister. The International Criminal Court (ICC) then brought a case against six prominent Kenyans for inciting the violence, including Kenyatta who was accused of funding Mungiki.

New legal framework

In 2010, a new constitution introduced a devolved system of government with 47 counties. Yet instead of preventing violence, this created a multi-layered contest during the 2013 election cycle.

Northeast Kenya and the former Coast Province witnessed ethnic clashes over land and county politics. Local officials funded vigilante groups to mobilise votes.

Elsewhere, the presidential contest caused conflict. In Nyanza, the vigilante groups American Maine, which was supporting Odinga, and China Group, supporting Kenyatta, clashed.

Central Kenya, the Kikuyu heartland, saw attacks on the Luo, Luhya and Nandi because they were perceived as being Odinga supporters. Meanwhile, violence continued between the Kikuyu and Kalenjin in the Rift Valley. The Mungiki were involved in both locations.

Have things changed?

These issues have yet to be resolved. The ICC cases were withdrawn after accusations of government obstruction. Politicians still exploit ethnic land grievances to gain votes, and vigilantes and militias still cause terror.

Kenya remains vulnerable. Odinga recently vowed to boycott the repeat election, and the incumbent Uhuru Kenyatta has attacked the judiciary. Read alongside protests against the Supreme Court ruling and demonstrations against the election commission, it is not hard to see how political violence could once again rear its ugly head.