The portion of the war depicted in the original anime, Mobile Suit Gundam depicts mainly the last few months of the 'One Year War', where only the introductory narration mentioned the earlier events including destruction of multiple space colonies and the dropping of an Island 3 type colony from orbit, resulting in the destruction of half of the human population. A short period in the first week of the war is known as the 'One Week Battle' or the 'One Week War', in which most civilian casualties are accrued by the indiscriminate use of WMDs and surprise attacks. The One Year War begins on January 3, UC 0079 (the Universal Century calendar begins some time after 2045 AD, according to the official timeline). The war is also known as the Zeon's War of Independence to the former soldiers of the Principality of Zeon. Its casualties, both military personnel and civilians were in the billions. The One Year War is the largest military conflict depicted in the Universal Century series, involving tens of thousand of mobile weapons, thousands of war ships and millions of combatants.
January 3rd, UC 0079 - January 1st, UC 0080