The Western Region election of 11 October 1965 was contested between Chief Samuel Ladoke Akintola's Nigerian National Democratic Party (NNDP, in alliance with the federal NPC) and the Awoist UPGA — the alliance of the Action Group rump (with Awolowo still in prison at Calabar) and the NCNC. The Electoral Commissioner Eyo Esua announced an NNDP landslide on 16 October. Western Region polling agents, election officers and over 400 UPGA supporters had been arrested in the preceding week; the result was rejected as comprehensively rigged by every credible foreign observer and by the British Daily Telegraph correspondent in Ibadan.
What followed — between October 1965 and 14 January 1966 — was the breakdown of state authority across Yorubaland. Operation Wetie (Yoruba: 'wet them') was the systematic petrol-bombing of NNDP supporters' houses, offices and persons by mobs aligned with the UPGA; NNDP enforcers responded in kind. Buses were burnt at Ibadan, Ife and Ilesa; markets at Akure and Owo were torched; the houses of the Olubadan and several Obas who had received Akintola were attacked. The Western Region Police, under federal control, refused to intervene; Federal Premier Balewa refused to declare a State of Emergency.
British and Nigerian estimates put deaths between October 1965 and mid-January 1966 at between 1,000 and 2,500 — the largest peacetime political violence event in Nigeria since amalgamation. The crisis radicalised the largely Igbo middle ranks of the Nigerian Army at Apapa and Kaduna: it was, in the explicit testimony of Major Chukwuma Nzeogwu at his court-martial, the precipitating event of the 15 January 1966 coup that killed Tafawa Balewa, Ahmadu Bello and Akintola himself, and ended the First Republic.