 He became an important player in the Perdicaris incident, in which Berber chieftain Mulai Ahmed er Raisuli kidnapped American expatriates Ion Perdicaris and his stepson, Cromwell Varley.Gummeré, a personal friend and former business partner of Perdicaris, initially advocated military action, but President Theodore Roosevelt and Secretary of State John Hay were more cautious, arguing that the situation in Morocco — which was maintaining a precarious independence due to the intrigues of foreign powers such as France, Britain, Germany, and Spain — made military action impractical.Gummeré met with the Ambassadors of France and Britain, and they agreed to help pressure the Sultan to meet Raisuli's demands.