Among the family archives preserved in Tartu one finds some volumes from the de la Barre family. Its most prominemt member during the Great Northern War was Lt. General Reinhold Johan de la Barre (166?-1724), who served under Armfelt in Finland, Sweden and Norway. One prominent letter from this collection was brought to light by Greta Wieselgren in an article in Svio-Estonica 1938. The letter was sent by Charles XII on 16 October 1718 and it contains a unequivocal instruction to de la Barre: he has to make sure that the King's orders are followed to the letter even if no one in the army survives. Parts of the letter echoes the King's sentiment towards the surrender at Perevolochna: those in command should not enter into discussions but rather give clear and distinct orders. They should not rely on reports from regimental commanders but look for themselves.
Wieselgren apparently never noted that the archive contains much more military material, both from the first years of the GNW and from 1719-1721. One notable item is a letter from the aide-de-camp Major G. W. Marcks von Würtemberg, written in Långå at 5 in the morning on 26 December 1718. The existence of this document has been known for a long time. In his book about Armfelt's campaign in Norway Gustaf Petri mentions that Marcks on the very same day wrote to Armfelt that the reports of the King's death had been confirmed. This letter never reached Armfelt, but the earlier message Marcks mentions that he sent de la Barre has - in Tartu.