Journey to Jaburo takes place during the One Year War, and depicts the crew of the White Base making their way from the Side 7 sector of space colonies to the Federation headquarters at Jaburo. The game starts at Amuro Ray's home of Side 7, where three Zaku mobile suits attack the Federation's prototype mobile suit weapons. Amuro, in the confusion, fights the Zaku units in the Gundam, and is assigned to the White Base as the Gundam's pilot. After the White Base leaves the colony, it is pursued by Char Aznable, "The Red Comet".
Char attacks the White Base during re-entry (where the power of the Gundam's beam rifle was revealed), which diverts them into the Zeon-controlled territory of North America. After going through many Zeon defenses (including Garma Zabi in Seattle), the White Base heads into Asia, where they battle Ramba Ral, an ace pilot who raised Sayla Mass when she was a child. After Ramba Ral commits suicide by jumping into Gundam's hand with a grenade, the White Base crew makes their way to Belfast for repairs.
After they leave Belfast, they eventually make it to Jaburo, where Char's "Mad Angler" squadron finds the location of the base, and launches a massive attack to conquer it. The Zeon forces are beaten back, and the White Base, now dubbed the "13th Autonomous Mobile Squadron", heads out into space.
Source: Wikipedia, "Mobile Suit Gundam: Journey to Jaburo)", available under the CC-BY-SA License.