The Swedes were not expecting to be attacked from the sea. The harbor of Salis, on the Livonian coast where the Salaca River meets the Gulf of Riga, was a Swedish naval base in the middle of Swedish-controlled territory, holding the squadron that was blockading Riga. The Polish-Lithuanian army moving through Livonia under Hetman Jan Karol Chodkiewicz had no fleet worth mentioning — a few captured ships, some hired merchant traders, a handful of bateaux. There was no plausible way they could threaten the Swedish warships at anchor. So on the night of 23 March 1609, when the wind began to blow inland and small burning ships drifted out of the darkness toward the line of moored Swedish vessels, no one was ready.
Jan Karol Chodkiewicz had been waging the Polish-Swedish War for nine years, mostly without enough money or men. His army was the same one that had annihilated a Swedish force three times its size at Kircholm in 1605 — a victory that should have ended the war but, because the Polish-Lithuanian Commonwealth had no funds to follow it up, had not. By 1609 he was still scraping together troops on his own credit and improvising. He had just captured the town of Pärnu on the Estonian coast, taking with it two Swedish ships and the cannons of Pärnu Castle. As his army marched south toward Riga he saw a possibility no Swedish admiral would have considered: he could improvise a navy out of what was at hand and use it to take out the blockade squadron at Salis.
What Chodkiewicz assembled would not have been called a fleet by anyone with a real one. The two Pärnu ships became his core, loaded with infantry from Samogitia — the western region of the Grand Duchy of Lithuania, an old land of forests and amber and people who knew the sea — and armed with cannons hauled out of Pärnu Castle. He bought five merchant ships, probably, from English and Dutch traders working the Baltic and gave them whatever guns he had. He added some boats and bateaux. To handle the actual sailing, he hired Livonian crew — the indigenous Baltic-Finnic people who had lived along this coast for centuries and knew its winds and shoals better than anyone. Possibly he bribed some sympathetic members of the Swedish garrison ashore. The whole assembly was, by warship standards, almost laughable. It was about to do something no one in the Baltic had seen before.
Fire ships had been used in Mediterranean and Atlantic warfare for generations — old hulks loaded with combustibles, set alight, and steered toward enemy fleets at anchor with skeleton crews who jumped clear at the last moment. One famous earlier example had come twenty-one years before, when English fire ships scattered the Spanish Armada in 1588. But in the Baltic in 1609, fire ships were essentially unknown. Chodkiewicz prepared four of them. Around midnight on 23 March he waited for the favorable inland wind, then sent the burning vessels drifting into the Salis roadstead. They hit exactly as designed: setting at least two Swedish warships alight as they pushed against the moored line of ships. The Swedes panicked. Sailors hacked at anchor cables to free their vessels and flee. Two ships burned and sank where they sat. The rest cut and ran for the open Gulf of Riga.
As the surviving Swedish ships fled the harbor they came under fire from Chodkiewicz's makeshift squadron waiting at the roadstead — the Samogitian-crewed Pärnu ships and the armed merchantmen. The Swedes did not stop to fight; their priority was to clear the burning anchorage. They reached the open gulf and ran for safer waters. The Samogitian ships, slower and not designed to chase warships, did not pursue. The whole port of Salis fell into Lithuanian hands intact, with all the Swedish stocks of weapons, ammunition, and food that had been stored there to support the Riga blockade. Two Swedish ships destroyed, no significant Polish-Lithuanian losses, an entire forward base captured and a blockade broken — for the cost of four expendable burning hulks and a few hours of darkness. It was a small operation, by the standards of the war, but its significance was disproportionate.
The combined Lithuanian victories at Pärnu and Salis halted the Swedish drive on Riga and bought the Commonwealth time. Chodkiewicz would continue to harass Swedish positions in Livonia for two more years before exhaustion and lack of funding pushed both sides to the truce of 1611. The truce held only six years; by 1617 the war restarted, and in 1621 the next Swedish king, Gustavus Adolphus, would land near Riga and capture the city in a quick siege — settling, in the Swedish account, the unfinished business of his uncle Charles IX. But Chodkiewicz's improvisation at Salis introduced fire ships to Baltic warfare. Over the next two centuries, fire ships would be used repeatedly in the Great Northern War, the Russo-Swedish wars, and the Anglo-Russian conflicts. Salacgrīva — the modern town that grew up around the old Salis port, at the mouth of the Salaca River about 100 kilometers north of Riga — is now a quiet Baltic resort with a yacht harbor and a salmon fishery. The shallow waters where Chodkiewicz's burning ships drifted in on the wind look much the same on a March night today.
The battle was fought at the mouth of the Salaca River near modern Salacgrīva, Latvia, at 57.76°N, 24.35°E — about 100 kilometers north of Riga along the eastern coast of the Gulf of Riga. From cruising altitude in clear weather the curve of the gulf coastline, the river mouth, and the broad shallow gulf are clearly visible. The Estonian island of Saaremaa lies across the gulf to the northwest. Nearest major airport is Riga International (EVRA), about 90 kilometers south. Tallinn (EETN) lies about 110 nautical miles north. Aircraft on Baltic transit routes between Helsinki (EFHK), Riga, and Vilnius (EYVI) often pass directly overhead.