You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Seven_Years%27_War

Context:
On the eastern front, progress was very slow. The Russian army was heavily dependent upon its main magazines in Poland, and the Prussian army launched several successful raids against them. One of them, led by general Platen in September resulted in the loss of 2,000 Russians, mostly captured, and the destruction of 5,000 wagons. Deprived of men, the Prussians had to resort to this new sort of warfare, raiding, to delay the advance of their enemies. Nonetheless, at the end of the year, they suffered two critical setbacks. The Russians under Zakhar Chernyshev and Pyotr Rumyantsev stormed Kolberg in Pomerania, while the Austrians captured Schweidnitz. The loss of Kolberg cost Prussia its last port on the Baltic Sea. In Britain, it was speculated that a total Prussian collapse was now imminent.

Question:
Identify a major Prussian loss to the Russians

Russians under Zakhar Chernyshev and Pyotr Rumyantsev stormed Kolberg in Pomerania