Some thousands of Boers with a considerable number of guns were known to be within the enclosure, and it was hoped that even if their own extreme mobility enabled them to escape it would be impossible for them to save their transport and their cannon.
Each of the British columns was about 2000 strong, making a total of 14,000 men with about fifty guns engaged in the operations.

A front of not less than ten miles was to be maintained by each force.

The first decided move was on the part of the extreme left wing, Smith-Dorrien's column, which moved south on Carolina, and thence on Bothwell near Lake Chrissie.

The arduous duty of passing supplies down from the line fell mainly upon him, and his force was in consequence larger than the others, consisting of 8500 men with thirteen guns.

On the arrival of Smith-Dorrien at Carolina the other columns started, their centre of advance being Ermelo.