The Somali invasion was initiated in May, when a force of between 3.000 and 6.000 WSLF fighters crossed the border to join forces of local resistance leaders. This invasion was therefore not merely an escalation of guerrilla warfare, but a well-planned strategic campaign. Many of involved WSLF fighters were actually officers of the Somali military, but resigned their commissions in order to take part in the operation.
The immediate target of Somali operations was crippling what was left of Ethiopia's economy by cutting the country's only railway line, which links Addis Ababa to Djibouti. In June 1977, guerrillas attacked a train and shortly afterwards blew up five bridges, bringing a halt to all traffic. Garrisons were attacked as well, especially the EtAF air base in Gode, in southern Ogaden, and the nearby barracks of the 5th Brigade 4th Division Ethiopian Army.
By 13 July 1977, the first out of four mechanized brigades of the regular Somali Army became active in Ethiopia, supported actively by the SAC. From 21 July, Somali MiG-21MFs - in part reportedly flown by a number of Iraqi and Syrian pilots - started a series of attacks against different points in Ethiopia. The SAC first tried to neutralize the remnants of the EtAF on the airfields nearby, and already on the first day of this counter-air operation an Ethiopian DC-3 was intercepted and shot down near Harer. Four days later, after more Somali air attacks, Gode fell to WSLF, and Mogadishu explained that so far at least eight Ethiopian aircraft were destroyed in air raids. Finding large amounts of supplies and arms in the five local military camps, the Somalis then turned to attack Sidamo and Bale, as well as Jijiga and Harer. Now the Ethiopian regime was forced to definitely do something about the whole affair.



