That same month, MFSO members marched together for the first time with Veterans For Peace at a national demonstration opposing a U.S. invasion of Iraq.
In February, 2003, 15 members of MFSO filed a lawsuit against President Bush and then-Secretary of Defense Donald Rumsfeld seeking to prevent a U.S. invasion of Iraq in the absence of a Congressional declaration of war.
Within two weeks of the beginning of the war in Iraq, the membership of MFSO doubled, with 400 member families at the end of March, 2003.
MFSO chapters have organized and built the voice of military families opposing the war in Iraq locally[where?][when?]
], with speaking programs, vigils, demonstrations, press conferences, meetings with elected officials, and many different kinds of creative actions.