Short answers, pulled from the story.
Tsar Ivan the Great issued a decree in 1493 to clear all buildings within 110 sazhens of the Kremlin wall, creating an empty field that eventually became Red Square. The area was originally called Pozhar, which translates to burnt-out place.
The linguistic shift from Pozhar to Krasnaya occurred gradually over centuries until the current name became official between 1661 and 1662. In archaic Russian, the word krasnaya meant beautiful before its meaning shifted to red during this period.
Italian architect Aloisio the New constructed a moat between 1508 and 1516 that connected the Moskva River with the Neglinnaya River. This defensive waterway reached depths of 9.5 to 13 meters and was lined with limestone.
Tsar Ivan the Terrible ordered a monumental church built in 1555 on the site where wooden Trinity Church once stood. This structure became Saint Basil's Cathedral by 1561 after being surrounded by fortifications.
Soviet authorities dismantled the Resurrection Gate in 1931 to allow military vehicles to pass through the square. The gate had been part of Kitai-Gorod fortifications since 1680 until it was later rebuilt as a replica in 1996.
The October Revolution Parade of 1941 took place while German troops besieged Moscow, and troops left Red Square directly for front lines after the ceremony. Military displays continued annually on May Day until 1969 and on Victory Day thereafter.