[6][citation needed] Despite her pacifist views, she wrote to the Manchester Guardian in November 1910, on behalf of the NUWSS, in defence of the suffragettes arrested during the Battle of Downing Street.

In 1915, together with such other prominent suffragists as Catherine Marshall and Agnes Maude Royden, she resigned from the NUWSS over its refusal to send delegates to the International Women's Congress at the Hague.

[citation needed] G. K. Chesterton criticised her pacifism in the 2 September 1916 issue of Illustrated London News: "Mrs. Swanwick ... has recently declared that there must be no punishment for the responsible Prussian.

If I were to propose, to the group which is supposed to inspire the Pacifist propaganda, that a man who burgled their strong boxes or pilfered their petty cash should suffer no punishment beyond failing to get the money, they would very logically ask me if I was an Anarchist.

"[8][note 1] After the war she maintained her internationalist views, opposing the punitive terms of the Treaty of Versailles and serving as the United Kingdom substitute delegate to the League of Nations.