When the Anglo-Boer War broke out on 10 October 1899, the boer forces had 21,000 men ready to invade the Colony of Natal. Ranged against them, the British had 13,000 men. The Boers, under the command of General Petrus Joubert, crossed the border into the Natal Colony and rapidly advanced to the Tugela river, laying siege to Ladysmith, some north of the river and entrapping some 8,000 British regulars. On 15 November a raiding party ambushed an armoured train at Frere, south of Colenso taking 70 prisoners including Winston Churchill. After another raiding party was surprised on 23 November at Willow Grange, to the south of Colenso, the Boers withdrew to a position behind the Tugela River.