The exploit encouraged Botha to plan a general attack, in co-operation with Viljoen, on a section of the railway each side of Belfast. It was made on January 7, 1901. The chief effort was against Belfast, where Smith-Dorrien was in command of a garrison too weak for effective resistance. Viljoen advancing from the north met with some preliminary success, but a fog prevented co-operation between him and Botha and the attack failed. The attacks on the other posts on the railway were repelled without much difficulty. The recrudescence of Botha, the intrusion of Beyers from the west, the hovering presence of Viljoen north of the Delagoa Bay Railway, and the rumour that an invasion of Natal was in contemplation to synchronize with raids beyond the Orange by De Wet, Kritzinger, and Hertzog, determined Lord Kitchener to try to sweep up and reduce the Eastern Transvaal. A force of five columns under the command of French was assembled a few miles east of the Elandsfontein-Pretoria Railway and began its advance on January 28. The general idea was that it should gradually extend its front, like the cone of dispersion of a shrapnel shell, between the diverging Natal and Delagoa Bay Railways, and then sweep eastward towards the Swaziland and Zululand borders; upon which Botha's commandos, if not already crushed by an enveloping movement on Ermelo, would be finally impaled. To assist French when he had traversed about one-half of the area, three columns were detailed to march southwards from the Delagoa Bay Railway on Ermelo. One of these columns was, however, sent away at the last moment under Paget to take part in the operations against De Wet in the Cape Colony. The combined strength of the seven columns against Botha was about 20,000 men, the majority of the combatants being mounted. A break back by Beyers and Kemp, who rejoined Delarey, was the opening incident of French's advance. The first objective of French's movement was the town of Ermelo, where Botha was acting as a sort of rearguard to cover the retreat of the fugitive burghers, who with their families and their stuff were endeavouring to escape from the Khakis. His contemplated attack on Natal was, at least for the time being, impracticable; and he set himself to the task of inflicting what damage he could on the threatening columns. He ascertained that Smith-Dorrien's column was approaching Lake Chrissie on February 5, and that the other column operating from the Delagoa Bay Railway under W. Campbell, was too far away to give it effectual support. The gap left by the withdrawal of Paget had not been filled up.