The First World War marked a crisis for the burgeoning women's movements in Europe and in the United States and tested the strength of the international bonds that the movement had been working to establish since the late nineteenth century. The outbreak of the war forced those active in the women's movement to make a choice between supporting their own country in a time of crisis and remaining true to the dominant vision of the "natural" pacifism and international sisterhood of all women. In most of the combatant nations, the call to arms polarized women, often dividing those who had worked closely together, with some rallying unproblematically to their nation's flag, others suspending their struggle for women's advancement and turning their backs on their international contacts "for the duration of the war", while yet others remained (or became) staunchly pacifist, developing and refining their ideological position as the war progressed.