However, Wilson made Colonel House his chief foreign policy advisor because Lansing privately opposed much of the Treaty of Versailles and was skeptical of the Wilsonian principle of self-determination.

[2] Lansing initially advocated for the United States to adopt a position of "benevolent neutrality" after the outbreak of World War I and opposed the blockade of Germany by the Allied powers.

Unlike Bryan he lacked a political base, though he had technical knowledge of international law and diplomatic procedure.

Wilson told Colonel House that as president he would practically be his own Secretary of State, and "Lansing would not be troublesome by uprooting or injecting his own views.

While Wilson set foreign policy directions almost entirely on his own, Lansing resented this treatment, and attempted to undermine the president in various ways.

According to Lester H. Woolsey, Lansing expressed his views by manipulating the work of the State Department to minimize conflict with Britain and maximize public awareness of Germany's faults.

In order to block this German ambition, he believed that the progress of the war would eventually disclose to the American people the purposes of the German Government; that German activities in the United States and in Latin America should be carefully investigated and frustrated; that the American republics to the south should be weaned from the German influences; that friendly relations with Mexico should be maintained even to the extent of recognizing the Carranza faction; that the Danish West Indies should be acquired in order to remove the possibility of Germany's obtaining a foothold in the Caribbean by conquest of Denmark or otherwise; that the United States should enter the war if it should appear that Germany would become the victor; and that American public opinion must be awakened in preparation for this contingency.

"[8] In 1916, Lansing hired a handful of men who became the State Department's first special agents in the new Bureau of Secret Intelligence.

Lansing was associate editor of the American Journal of International Law, and with Gary M. Jones was the author of Government: Its Origin, Growth, and Form in the United States (1902).

Lansing kept a voluminous archive of US government communications during WWI, which are a key resource on US thinking and decision making in this period.

During World War II the Liberty ship SS Robert Lansing was built in Panama City, Florida, and named in his honor.