Following the declaration of war against France and Britain by Italy on 10 June 1940, the East African Campaign began as military forces of the British Empire engaged the Italian East African Armed Forces Command (Comando Forze Armate dell'Africa Orientale) in Italian East Africa.
After a series of actions in 1940, British colonial forces from Anglo-Egyptian Sudan invaded the territory and eventually a salient formed around the Baro River.
In March 1941, the Italian forces began to withdraw from the salient under increasing pressure.
On 8 March the first battalion of the Belgo-Congolese expeditionary force marched from Kurmuk towards the Italian-held town of Asosa.

The expeditionary force attacked three days later in conjunction with troops of the King's African Rifles (KAR), forcing the garrison to retreat to Gidami.
Next, the Belgians and Congolese began attacking the town of Gambela directly from the west while two companies of the 2/6 KAR under Captain J. W. E. Mackenzie were sent to outflank it and cut off its link with the Italian headquarters at Saïo under the command of General Carlo De Simone.
The Belgians were concerned that the Italians might attempt an offensive over the weakly defended Sudanese border; by taking Gambela they could force Gazzera's forces in western Ethiopia into a defensive position.
On 22 March, the KAR companies attacked but withdrew to the south when a planned Belgian assault failed to materialise.
The Italians were nevertheless surprised by the flanking manoeuvre and retreated to Saïo.
Following the declaration of war against France and Britain by Italy on 10 June 1940, the East African Campaign began as military forces of the British Empire engaged the Italian East African Armed Forces Command (Comando Forze Armate dell'Africa Orientale) in Italian East Africa. After a series of actions in 1940, British colonial forces from Anglo-Egyptian Sudan invaded the territory and eventually a salient formed around the Baro River. In March 1941, the Italian forces began to withdraw from the salient under increasing pressure. On 8 March the first battalion of the Belgo-Congolese expeditionary force marched from Kurmuk towards the Italian-held town of Asosa.
The expeditionary force attacked three days later in conjunction with troops of the King's African Rifles (KAR), forcing the garrison to retreat to Gidami. Next, the Belgians and Congolese began attacking the town of Gambela directly from the west while two companies of the 2/6 KAR under Captain J. W. E. Mackenzie were sent to outflank it and cut off its link with the Italian headquarters at Saïo under the command of General Carlo De Simone. The Belgians were concerned that the Italians might attempt an offensive over the weakly defended Sudanese border; by taking Gambela they could force Gazzera's forces in western Ethiopia into a defensive position. On 22 March, the KAR companies attacked but withdrew to the south when a planned Belgian assault failed to materialise. The Italians were nevertheless surprised by the flanking manoeuvre and retreated to Saïo.
Siege of Saïo