The newly-formed Earth Alliance declared war against PLANT on the 11th, and launched a combined fleet toward PLANT to subdue the rebellious coordinators once and for all…

Yet despite their vast numerical superiority, the Alliance forces was being decimated by ZAFT. Facing with defeat and failing their strategic goal, Admiral William Sutherland onboard Alliance carrier Roosevelt ordered the Peacemaker Nuclear Task Force to launch, targeting the illegal agricultural colonies of PLANT. Intending to complete their mission of end PLANTs food production capability no matter what.

A nuclear warhead slipped through ZAFT’s interception, and destroyed Junius-7, killing 243,721 people in one fell swoop.

-Below are from Gundam Seed RE, the manga.