Ukrainians will mark their independence from the Soviet Union on Wednesday, the same day they'll mark a half year of war. But authorities have banned them from celebrating because of a heightened risk of attack.

Residents of the capital, Kyiv, came out on Monday to look at Russian weapons destroyed in the fighting. "They must know their history," one father said of his children.

Russians marked an anniversary of their own on Monday. They celebrated National Flag Day, which commemorates the raising of the tricolor in 1991 after an attempted coup. Separatists in Ukrainian cities the Russians have captured joined in.

Russian forces have been surprised by the strength of the resistance. Ukrainian troops are trying to retake ground in the east and the south. Some, in the Kherson region, attacked a bridge the Russians have used to bring in supplies.

Ukrainians want to take back territory lost in 2014. On Tuesday, Ukrainian leaders are holding an international summit on the Crimean Peninsula, online. Foreign Minister Dmytro Kuleba said "Crimea was, is and will be Ukraine."