In 1905, Japan forced Russia to surrender in the Russo-Japanese War. Russia ended up surrendering to Japan, but many people believed that if Russia didn't surrender, they could have easily won the war.
The Russo-Japanese War started because Russia and Japan had a disagreement over who would get some parts of land. Both of them wanted certain parts of land for trade and they couldn't come to an agreement on it, so a war started between them.
After Japan made Russia surrender, the Russian people were angered at Nicholas II, because he was the one who felt like Russia needed to surrender. The people believed that Russia could have won the war since the Japanese economy was terrible and declining and they had less soldiers than Russia.