The Allies planned a large offensive in the Macedonian front for the middle of August to support Romania's entry into the war and pin down as many Bulgarian forces as possible.

The Bulgarian high command suspected an impending offensive, and the fighting around Doiran that erupted on 9 August only confirmed these suspicions.

The Struma operation on the eastern flank by the Bulgarian Second Army under General Todorov was a huge success, mainly because the Greek government ordered their troops not to resist.

General Boyadzhiev agreed to attack but had concerns regarding the final results of the offensive because his army was scattered on a 140 km front and lacked enough mountain and heavy artillery.

The Serbians were reinforced with new artillery constantly and fresh troops thanks to the railway that reached the battlefield, while the Bulgarians soon began depleting their ammunition stocks.