Since the surrender of Cronje on February 27th, Lord Roberts has been completing his supplies, and probably making good the damage to his transport caused by the loss of a convoy on the Riet River. He has also brought up the Guards Brigade as a reinforcement. A few days ago the camp was moved forward from Paardeberg to Osfontein, and beyond Osfontein the Boers were observed collecting their troops from day to day and extending their position, which ran roughly north and south across the Modder. Yesterday Lord Roberts advanced to the attack with three and a half infantry divisions, a cavalry division and a brigade of mounted infantry. The cavalry, followed by an infantry division, turned the enemy's left flank, and by noon the enemy's army was in full retreat towards the north and east, pursued by the British. The Boers have this time not ventured to stand to fight. They have seen themselves assailed in front by a force which must have greatly outnumbered them at the same time that their flank was turned by a force as mobile as their own. Their precipitate retreat coming after their late defeats must increase their demoralisation, and it will hardly be practicable for them to make a fresh stand east of the Free State Railway. Lord Roberts will be on the railway with the bulk of his force by Saturday or Sunday, and his presence there will complete the break up of the Boer defences of the Orange River. The situation of the Boers is now, as far as it depends on themselves, desperate. They can hardly collect forty thousand men for a decisive battle, and are confronted by two armies, each of which has that strength, the one nearing Bloemfontein, the other at Ladysmith. Lord Roberts, when he reaches the railway, will probably call up from the Orange River such additional forces as are not required as garrisons in Cape Colony. His numbers can be fed by constant small reinforcements, while the Boers have no means of increasing their numbers. With each succeeding week, therefore, the British will grow stronger and the Boers fewer. The utmost that the Boer commander-in-chief can expect to accomplish is to delay that advance to Pretoria which he cannot prevent.