On 22 July 1700 Erik Dahlbergh wrote to Charles XII, informing him that General Vellingk "who had been standing here so long without doing anything explicit against the enemy" despite every possible preparation having been made for a crossing of the Düna. Now the Saxons had been reinforced and the on the 17th they had crossed the river at Pröbstingshoff (Sprēstiņi). Vellingk had moved towards the enemy the following day and on the 21st attempted an attack, but finding the Saxon position too strong he soon retreated. Dahlbergh was very unhappy, telling the King that he saw no other means of defending Riga than asking Vellingk for reinforcements. On 27 July Vellingk wrote to the Chancery in Stockholm, stating that Vellingk had retreated "in confusion" with the cavalry and 1,500 foot, but the rest of the infantry and some cavalry had managed to enter Riga.
A list preserved elesewhere gives detailed information about the reinforcements received - about 5 100 officers, non-commissioned officers and soldiers from the Finnish infantry regiments (Close to 700 from the Tavastehus infantry, close to 1,000 from the Åbo infantry, about 900 from the Savolax infantry, about the same from the Björneborg infantry, about 700 from the Vyborg infantry and above 800 from the Nyland infantry).
Sources:
LVVA, fond 7349, op. 1, vol. 72
Krigsarkivet, Krigshandlingar. Stora nordiska kriget. Avd. 19, vol. 1