Romocki was active in the Szare Szeregi (Gray Ranks) organisation from 1940 onwards and during the Warsaw Uprising he was the commander of the Rudy Company of the AK Zośka Battalion.

After 11 August, when Wola fell, Romocki and the entire Zośka Battalion relocated to Warsaw Old Town ("Starówka" or "Stare Miasto" in Polish), where they fought valiantly for the next three weeks.

By the end of August the Germans were bombing the encircled Old Town from the air every 15–20 minutes while their artillery also shelled the area throughout the day.

Zośka lost so many soldiers during the first month of the uprising that Romocki, despite himself being wounded in the face during the escape, became commander of the whole battalion after it relocated to the city centre.

On 15 September 1944, units of the LWP made their first attempt to cross the river and link up with the insurgents in Czerniaków, in spite of Joseph Stalin's ban.