The Italians mined the 40 mi (64 km)-long Saïo–Gambela road that led to the Saïo Plateau 4,000 ft (1,200 m) above the surrounding area.
The Belgians began slowly advancing but encountered Italians at the Bortai Brook, which ran perpendicular to the road.
The Belgians were strengthened by the arrival of a Stokes mortar company and another battalion.
Numbering at 1,600 soldiers and 600 non-combatant porters, they lacked the strength to seize the plateau.
With the Italians receiving reinforcements of troops retreating from the east, the Belgians decided to keep the initiative to disguise their small numbers.

Three days of cold weather and rain preceded the offensive.
On 15 April, Lieutenant Colonel Edmond van der Meersch led an attack on the brook.
A Belgian lieutenant scouting in no man's land was ambushed and killed.
A Belgian sergeant caught three Italian officers at gunpoint but lowered his revolver when they claimed to be English, thinking the KAR might have dispatched a liaison party to the area.
He was then shot by snipers concealed in the bush.
A battle ensued in which four Congolese soldiers were killed.
Three Italians and an estimated 40 Eritrean Ascari were killed, with approximately 70 Ascari wounded.

During the ensuring stalemate, the Belgians studied the Italians' tactics; they would post pairs of snipers and artillery spotters in trees guarded at the bases by infantry squads.
Their artillery barrages were usually avoided by Belgian patrols, though they would continue up to an hour after they withdrew.
On 21 April, the Italians launched a large counterattack.
After a two-hour bombardment, Eritrean troops armed with automatic weapons and hand grenades and covered by Galla snipers penetrated the Belgians' left and right flanks.
With Van der Meerch's battalion suffering the brunt of the assault, the Belgians retreated behind a pair of hills that obscured them from Italian observers, which the latter then seized.
The Italians mined the 40 mi (64 km)-long Saïo–Gambela road that led to the Saïo Plateau 4,000 ft (1,200 m) above the surrounding area. The Belgians began slowly advancing but encountered Italians at the Bortai Brook, which ran perpendicular to the road. The Belgians were strengthened by the arrival of a Stokes mortar company and another battalion. Numbering at 1,600 soldiers and 600 non-combatant porters, they lacked the strength to seize the plateau. With the Italians receiving reinforcements of troops retreating from the east, the Belgians decided to keep the initiative to disguise their small numbers.
Three days of cold weather and rain preceded the offensive. On 15 April, Lieutenant Colonel Edmond van der Meersch led an attack on the brook. A Belgian lieutenant scouting in no man's land was ambushed and killed. A Belgian sergeant caught three Italian officers at gunpoint but lowered his revolver when they claimed to be English, thinking the KAR might have dispatched a liaison party to the area. He was then shot by snipers concealed in the bush. A battle ensued in which four Congolese soldiers were killed. Three Italians and an estimated 40 Eritrean Ascari were killed, with approximately 70 Ascari wounded.
During the ensuring stalemate, the Belgians studied the Italians' tactics; they would post pairs of snipers and artillery spotters in trees guarded at the bases by infantry squads. Their artillery barrages were usually avoided by Belgian patrols, though they would continue up to an hour after they withdrew. On 21 April, the Italians launched a large counterattack. After a two-hour bombardment, Eritrean troops armed with automatic weapons and hand grenades and covered by Galla snipers penetrated the Belgians' left and right flanks. With Van der Meerch's battalion suffering the brunt of the assault, the Belgians retreated behind a pair of hills that obscured them from Italian observers, which the latter then seized.
Siege of Saïo