Operation Odessa was the Earth Federation Force's first major offensive campaign on Earth.
A chance to strike back opened up with the death of Garma Zabi. Operation Odessa used 30% of the Federation Army to take out the Zeon mining facilities in the Odessa region, the lynchpin of the Principality supply network. Launched in early November, the objective of the campaign was to capture the Zeon mining facilities at Odessa and drive Zeon forces out of Europe and Asia. The operation was launched on November 7, ending two days later in victory for the Earth Federation. This was remarkable for the fact that the Earth Federation Forces consisted almost entirely of conventional forces, tanks and aircraft, and yet managed to defeat the Zeon force consisting of many mobile suits. The Earth Federation did have a small number of mobile suits at the battle, but they were mainly used in mopping up operations, and contributed relatively little to the battle. Operation Odessa marks the turning point of the One Year War, the beginning of the end for Zeon's forces in Europe and Asia. However, the leader of the Zeon mining operations Colonel M'Quve had enough mining material sent to the Zeon homeland allowing Zeon to continue the war without the danger of supply shortages. This battle was the largest and the bloodiest battle on Earth, where Earth Federation relied heavily on conventional weapons such as tanks, bombers, air fighters and a few amounts of MSs (30 units) and in large numbers of troops (amounted 3,700,000 troops) lost more lives compared to much smaller but much powerful Principality of Zeon (having only small amounts of air fighters, tanks, bombers, cannon and artillery but huge amounts of MS which are more advantageous against Earth Federation's forces) but Earth Federation won the battle. (The complete statistics of the battle can be seen on Odessa)
In the TV series version of Mobile Suit Gundam the White Base played a more important role. M'Quve had the aid of a traitor within the Federation General Elron where through the associate Judoc planned to sabotage the operation by holding back the troops led by Elron to allow M'Quve's forces to attack the troops belonging to General Revil. White Base pilots Amuro Ray and Sayla Mass accidentally witness Judoc's Federation-commissioned plane leave a Zeon base without incident and they follow it and it leads to Elron and Judoc's arrest allowing Elron and Revil's forces to easily overpower M'Quve's unsuspecting forces. In desperation, M'Quve tried to break the Antarctic Treaty by launching a nuclear missile but Amuro and the Gundam are able to disable it. From there, the determined Earth Federation Forces emancipated Europe, Asia and eventually North America. The remaining Zeon troops regrouped for a massive assault on Jaburo base, hoping to kill the heart of the Federation.