Concerned with this turn of events the Bulgarian high command convinced its allied German high command that a demonstration of force was necessary on the Macedonian Front in order to shorten the Central Powers front line and carry out a preemptive strike against the Entente forces in Salonika that were preparing an offensive of their own, hoping to assist Romania. So on 17 August the Bulgarian First Army began the Chegan Offensive and took Lerin but after ten days of fighting failed to achieve its objectives. On 27 August the operation was called off and the army ordered to dig in on the positions between Lake Petursko, Lake Ostrovo an along the ridge of the Malka Nidzhe mountain it had occupied.