On January 3rd, U.C. 0079, the Jion Archduchy declared war on the Earth Federation Government. Immediately after the declaration of war ends Jion forces simultaneously attack Sides 1, 2, and 4. The unrestrained use of ABC (atomic, biological, and chemical) weapons resulted in millions of civilian casualties in mere seconds. In some cases the carnage didn't stop there. Jion forces commandeered one of the heavily damaged sides and caused it to fall on Earth. The resulting blast, three million times as powerful as the blast that destroyed Hiroshima, completely destroyed 16% of the continent of Australia, and drastically changed the Earth's climate. Even though the Salamis and Magellan warships were easy prey for the Jion's Zakus most of the time, the EMF still managed to inflict heavy casualties on the Jion Archduchy, both military and civilian. By January 10th 25% of the total human population had been killed. Taking advantage of the heavy confusion among the EMF ranks, Jion forces invade Earth and manage to capture a large part of the surface. A few days later the Ruum Campaign, the largest space battle in history, took place near Side 5. The mobility of the Jion's Zaku proves to be the deciding factor of the day, and the battle becomes a resounding defeat for the EMF. During the battle a young Jion pilot named Char Aznable distinguished himself by single- handedly destroying 5 EMF cruisers, earning himself the title "the Red Comet" and a promotion in rank.
On January 16th a peace meeting between the Jion Archduchy and EFG was held in Antarctica. The resulting treaty, called the Antarctica Treaty, banned both sides from using ABC weapons against the other's civilian populations. By now, however, both sides' military forces had been so exhausted that neither one could gain a true advantage. The war degraded into a stalemate. The Jions took advantage of the lull in combat by consolidating their gains and using the captured EMF forces to replenish their war potential. The Jions also began stationing specialized mobile suits for localized warfare around the globe.
The EMF, on the other hand, implements their "V-plan." A secret research base on Side 7 begins to work on developing a mobile suit for the EMF that is superior to anything the Jions have. To aid in this task, two new discoveries have been made available to the Side 7 engineers. The first is a special metal from the moon called "Lunar Titanium," which is several times stronger than any metal previously known. The second new development was beam weapon technology, which was a by-product of Minovski particle research that the Jions never bothered to pursue. This new technology could be used to create a MS weapon that had the equivalent power of huge battleship weapons. This new MS rifle was called the Beam Rifle. A further refinement of this technology led to the development of the Beam Saber. The Beam Saber was a melee weapon which could cut through several feet of steel in less than a second. Unfortunately, both these weapons had bugs in them that occasionally caused them to loose power or break down completely. These problems would not be solved until the closing days of the One Year War.
The result of the Side 7 engineers' efforts was well worth the wait, however. In July of U.C. 0079 the prototype RX-78 Gundam MS was completed. The Gundam was the best thing that could have happened to the EMF at the time. No Jion MS could penetrate the Gundam's armor or match its firepower. The RX-78 Gundam would turn the tide of battle in the EMF's favor, and eventually contribute greatly to the defeat of the Jion Archduchy. Kido Senshi Gundam, the first Gundam series, begins at this point.