Meanwhile, across the river on the east bank of the Vorskla, Russian forces were gathering. Menshikov, the most aggressive of Peter's generals, commanded these troops from his headquarters in the village of Krutoy Bereg, while Sheremetev with the main army was approaching from the northeast. Menshikov's orders were to observe^ the Swedes across the river and to do what he could to assist the garrison inside Poltava. The latter mission was not easy. Between the low east bank where the Russians were and the steep west bank which rose more than 200 feet to the walls of the town, the river wandered through a maze of marshes impassable to a large army and difficult even for small parties. Several times the Russians tried to send reinforcements directly across to Poltava, even attempting to build a road with sacks of sand, but these efforts failed. The communication problem was finally solved by putting messages inside hollow cannonballs and firing them back and forth across the river between Menshikov and Colonel Kelin.
The river war continued. Parties of horsemen, Russians and Swedes, rode along the opposite sides of the river, patrolling and watching for any sign of movement on the other bank, trying to snatch prisoners from whom they could gain some intelligence. At the end of May, Sheremetev arrived in the Krutoy Bereg camp with his masses of Russian infantry, but, despite their numerical superiority, the Russian generals were uncertain what to do. They learned from Colonel Kelin that his supply of gunpowder was dangerously low, that Swedish mining under his walls was about complete, mat he estimated he could not hold out beyond the end of June. Menshikov and Sheremetev did not want the town to fall, but were not prepared to provoke a general engagement. Certainly, nothing so dramatic and decisive as an attempted mass crossing of the Vorskla in the teeth of determined Swedish opposition had any appeal. Nevertheless, knowing that the decisive moment was approaching, Menshikov sent word to Peter, who was on his way from Azov across the steppe, to hurry. The Tsar replied on May 31 that he was coming as fast as he could, but that rather than lose an advantage which might present itself, the army should if necessary fight without him. As Poltava still held out, the Russian generals decided to wait a little longer.
On June 4, Peter arrived and while his habit had been to appoint one of his generals as commander-in-chief and to take only subordinate rank himself, he now assumed supreme command. Peter brought with him 8,000 new recruits to add to the troops now preparing for battle. His arrival infused new spirit into the soldiers who were skirmishing vigorously at all points along the river. On June 15, a surprise Russian attack on Stary Senzhary inside the Swedish-occupied region freed 1,000 Russian prisoners taken the previous winter at Veprik, and Cossack horsemen loyal to the Tsar broke in and plundered a section of the Swedish baggage train.
Now, the great trial of arms was drawing near. The two armies were in close proximity, each commanded by its monarch. Both realized that the climax was at hand. Charles, confined in an ever narrowing space, would eventually have to try to break out. Peter understood and accepted this. The Tsar, who in the past had been unwilling to risk everything on a single battle, was steeling himself to meet the final test. His strategy had borne fruit. The enemy was isolated. Across Charles' line of retreat to Poland lay Field Marshal Goltz with a powerful force which could either prevent the advance of any relieving force or cut off the retreat of Charles himself. And Peter's army on the Vorskla was now twice as strong as Charles'. It was therefore with grim optimism that Peter wrote to Apraxin on June 7, after joining the army, "We have gathered close to our neighbors and, with God's help, we shall certainly this month have our affair with them."
Within a few days of his arrival, Peter summoned all his generals to his tent and together they examined the facts. It was only a matter of time before Poltava fell. In Swedish hands, the city would serve as a rallying point for the potential reinforcements which Charles hoped—and Peter feared—might join the Swedish King and even at this late date open the road to Moscow. These stakes were high enough to force Peter and his generals to a climactic decision: To relieve pressure on the Poltava garrison and prevent the city's fall, the main Russian army would have to be brought into play. A major, and very possibly a decisive battle would have to be fought no later than June 29 in order to save Poltava. By the 29th, Peter expected to have concentrated all his forces; not only Skoropadsky's Cossacks would be present, but 5,000 Kalmucks riding behind their khan Ayuk. But the army could not be used as long as it remained on the east bank of the Vorskla: it would have to cross to the west bank. Once on the same side of the river as the Swedes, Peter could launch a flank attack on the Swedish lines besieging the city. At the very least, even if a major battle was not joined, the presence of the Russian army would force to Swedes to divert much of their strength from their positions before Poltava and thus relieve the pressure on the city. In addition, a position on the Swedish flank would permit the Tsar to bring to bear the considerable Russian field artillery. His guns, now silent and useless across the river, would be able to fire into the Swedish camp.
Peter next had to determine where and when to cross. There was no thought of attempting to force a passage across the wide, marshy river in the teeth of strong opposition, as Charles had frequently done. Instead, Peter decided to mount diversionary feints all along the river front both north and south of Poltava to distract the Swedes, while the main army would cross at Petrovka, seven miles north of the town where there were places shallow enough for horsemen to ride across. Ronne would cross first with ten regiments of cavalry and dragoons, followed by ten regiments of infantry under Hallart. Once this force had cleared a bridgehead and successfully entrenched itself in a camp at Semenovka a mile below the ford, Peter would bring the main army across. Ronne and Hallart quickly moved their troops into position and, on the night of June 14, they attempted a crossing, which was repulsed. But the Tsar was not to be denied. From Poltava, Colonel Kelin sent word that he could not hold out much longer and Peter decided to try again immediately.
The Swedes were fully aware of the impending crossing at Petrovka. On the nights of June 15 and 16, the Swedish army remained at battle stations. Rehnskjold was in command of the Swedish forces—ten cavalry regiments and sixteen infantry battalions—which would meet the Russians as they crossed the river. His tactics would be to permit a part of the Russian army to cross and then, while the Swedes still enjoyed a numerical advantage, attack and drive the Russian vanguard back into the river. Charles remained in command of the troops before Poltava and along the river south of the city. His intention was to wait there until the battle began and he had determined that no major Russian force was crossing south of the city; then, he would ride north to join Rehnskjold at Petrovka. It was a logical formula for victory. But before this Swedish plan could be executed, disaster struck.
June 17, 1709, was Charles XII's twenty-seventh birthday. In his nine years of active campaigning, the King had led a charmed life relative to injury in battle. Although he had been hit by a spent bullet at Narva and had broken his leg in Poland, he had never been seriously wounded. Now, at the most critical moment of his military career, his luck suddenly deserted him.
At daybreak that morning, the King rode to the village of Nizhny Mliny south of Poltava to inspect the Swedish and Cossack positions along the Vorskla. He had good reason: The battle portending north of the city when the Russians crossed would draw most of the Swedish army in that direction. Before permitting this maneuver, Charles wanted to make sure that the river defenses to the south were sufficiently strong to repel any crossing in that region. On the opposite bank, as part of Peter's diversionary tactics, a Russian cavalry force was doing its best to keep the Swedes distracted. One Russian attempt to cross had already been repulsed.