Emperor Nikephoros sends to Sviatoslav his agent, Kalokyros, in 967 or 968 with the task of talking Sviatoslav into assisting Constantinople in a war against Bulgaria.

Sviatoslav is paid fifteen thousand pounds of gold and sets sail with an army of fifty thousand men, including thousands of Pecheneg mercenaries.

According to the Russian Primary Chronicle, while Sviatoslav was pursuing this campaign against the First Bulgarian Empire, the Pechenegs (in all probability, bribed by Nikephoros) invade Rus and besiege his capital of Kiev.

While the besieged suffer from hunger and thirst, Sviatoslav's general Pretich deploys his druzhina, his personal guard, on the opposite (left) bank of the Dnieper, not daring to cross the river against the larger Pecheneg force.

Sviatoslav's mother Olga of Kiev (who is in Kiev together with all of Sviatoslav's sons), reduced to extremes, contemplates surrender, if Pretich does not relieve the siege within one day.

She is anxious to send word about her plans to Pretich.

At last, a boy fluent in the Pecheneg language volunteers to venture from the city and urge Pretich to action.

Pretending to be a Pecheneg, he goes about their camp, as if searching for a lost horse.

When he attempts to swim across the Dnieper, the Pechenegs discover his subterfuge and start shooting at him, but to no avail.

When the boy reaches the opposite bank and informs Pretich about the desperate condition of the Kievans, the general decides to make a sally in order to evacuate Sviatoslav's family from the city, for fear of his sovereign's anger.

Early in the morning, Pretich and his troops embark on boats across the Dnieper, making great noise with their trumpets.

The besieged start cheering, and Olga ventures out of the city towards the river.

The Pechenegs, thinking that Sviatoslav is returning with his great army, lifts the siege.

The Pecheneg leader then decides to confer with Pretich and asks him whether he is Sviatoslav.

Pretich admits that he is only a general but warns the Pecheneg ruler that his unit is a vanguard of Sviatoslav's approaching army.

As a sign of his peaceful disposition, the Pecheneg ruler shakes hands with Pretich and exchanges his own horse, sword and arrows for Pretich's armor.

As soon as the Pechenegs retreat, Olga sends a letter to Sviatoslav reproaching him for his neglect of the family and people.

Upon receiving the message, Sviatoslav speedily returns to Kiev and thoroughly defeats the Pechenegs, who are still threatening the city from the south.