In January 1915, she became involved in the Woman's Peace Party and was elected national chairman. Addams was invited by European women peace activists to preside over the International Congress of Women in The Hague, 28–30 April 1915, and was chosen to head the commission to find an end to the war. This included meeting ten leaders in neutral countries as well as those at war to discuss mediation. This was the first significant international effort against the war. Addams, along with co-delegates Emily Balch and Alice Hamilton, documented their experiences of this venture, published as a book, "Women at The Hague" (University of Illinois).