The Saxons at length united their force with the Swedes; at the same time the Imperialists, under the Count de Tilly, invaded Saxony, and captured several towns, including _Leipsic_. The Swedish and Saxon armies advanced against the invaders, and this movement was followed by the decisive battle of _Leipsic_, in which COLONEL HEPBURN'S REGIMENT took an important part.[22] Having passed the night in order of battle, at day-break, on the morning of the memorable 7th of September, 1631, divine service was performed in the Swedish army, and the troops afterwards advanced against the enemy. The Swedes took the right, and the Saxons the left. The advance guard was composed of three regiments, two Scots and one Dutch, led by three Scots colonels; and HEPBURN'S SCOTS BRIGADE formed part of the reserve, which was commanded by Colonel Hepburn. The engagement commenced about mid-day; and after a tremendous cannonade, the cavalry of both armies advanced and engaged in a series of charges, in which the Swedish and Finland horse had the advantage; and the King was enabled to change his position so as to avoid the evil effects of a high wind and clouds of dust which nearly blinded his soldiers. At length the enemy attacked the Saxons on the left with great fury, and drove them out of the field. The Imperialists then directed their main force against the Swedes, and a detachment from the Scots regiments highly distinguished itself in a conflict with the enemy's cavalry.[23] During the heat of the conflict HEPBURN'S SCOTS BRIGADE was moved from the rear of the centre to the left flank, which had become exposed by the flight of the Saxons. Immediately afterwards two columns of the enemy were seen coming down upon the left of the Swedish army, and the King ordered HEPBURN'S SCOTS BRIGADE to wheel to the left and confront the enemy. Before this movement was executed, the Imperialists were within musket shot; in a moment the artillery on both sides opened a tremendous cannonade; this was followed by two volleys from the musketeers, and the next moment HEPBURN'S pikemen went cheering to the charge with distinguished bravery, and, breaking in upon the front of the first column, drove it back with terrible confusion and slaughter. Meanwhile HEPBURN'S right wing of musketeers, commanded by Colonel Monro, fell with great fury upon the enemy's troops which protected the cannon and captured the guns. The slaughter would have been great, but the ground where the battle was fought being very dry, and newly ploughed, and the wind high, the clouds of dust favoured the escape of the enemy.[24] When HEPBURN'S BRIGADE was attacking the enemy's columns, the King sent the Blue Brigade and a body of musketeers to its assistance; but before the arrival of these reinforcements the Scots were triumphant. The Imperial columns being broken, the Swedish horsemen pursued the fugitives until dark and made great slaughter.