Julian Wadleigh joined other left-wing socialist supporters of the New Deal in forming the Harold Ware Group. Established by Harold Ware, the son of Ella Reeve Bloor, the discussion group included Alger Hiss, Nathaniel Weyl, Laurence Duggan, Harry Dexter White, Nathan Witt, Marion Bachrach, Henry H. Collins, Lee Pressman and Victor Perlo. Ware was working very close with Joszef Peter, the "head of the underground section of the American Communist Party." It was claimed that Peter's objective was for its members to "influence policy at several levels" as their careers progressed".

Susan Jacoby, the author of Alger Hiss and the Battle for History (2009), has pointed out: "Chambers, among others, would testify that the eventual penetration of the government was the ultimate aim of a group initially overseen in Washington by Hal Ware, a Communist and the son of Mother Bloor... When members did succeed in moving up the government ladder, they were supposed to separate from the Ware organization, which was well known for its Marxist participants. Chambers was dispatched from New York by underground Party superiors to supervise and coordinate the transmission of information and to ride herd on underground Communists - Hiss among them - with government jobs."

Whittaker Chambers later explained in Witness (1952): "The Washington apparatus to which I was attached led its own secret existence. But through me, and through others, it maintained direct and helpful connections with two underground apparatuses of the American Communist Party in Washington. One of these was the so-called Ware group, which takes its name from Harold Ware, the American Communist who was active in organizing it. In addition to the four members of this group (including himself) whom Lee Pressman has named under oath, there must have been some sixty or seventy others, though Pressman did not necessarily know them all; neither did I. All were dues-paying members of the Communist Party. Nearly all were employed in the United States Government, some in rather high positions, notably in the Department of Agriculture, the Department of Justice, the Department of the Interior, the National Labor Relations Board, the Agricultural Adjustment Administration, the Railroad Retirement Board, the National Research Project - and others."

In March 1936, Wadleigh transferred to the State Department, where he worked at the Trade Agreements division. During this period he passed documents to Soviet agents. However, he became very concerned with the Great Purge that was taking place in the Soviet Union. He brought this up with his controllers in the United States. In August 1939 Joseph Stalin and Adolf Hitler agreed to sign the Nazi-Soviet Pact. Wadleigh was so upset by this decision he refused to cooperate with Soviet agents.

In August 1939, Isaac Don Levine arranged for Whittaker Chambers to meet Adolf Berle, one of the top aides to President Franklin D. Roosevelt. After dinner Chambers told Berle about government officials spying for the Soviet Union: "Around midnight, we went into the house. What we said there is not in question because Berle took it in the form of penciled notes. Just inside the front door, he sat at a little desk or table with a telephone on it and while I talked he wrote, abbreviating swiftly as he went along. These notes did not cover the entire conversation on the lawn. They were what we recapitulated quickly at a late hour after a good many drinks. I assumed that they were an exploratory skeleton on which further conversations and investigation would be based."

According to Levine the list of "espionage agents" included Wadleigh, Alger Hiss, Donald Hiss, Laurence Duggan, Lauchlin Currie, Harry Dexter White, John Abt, Nathan Witt, Lee Pressman, Noel Field and Frank Coe. Chambers also named Joszef Peter, as being "responsible for the Washington sector" and "after 1929 the "head of the underground section" of the American Communist Party.

Soon after the outbreak of the Second World War Wadleigh went to work for Leo Pasvolsky, Special Assistant to the Secretary of State Cordell Hull on the problems of postwar economic policy. In 1943, Wadleigh was transferred to the Office of Foreign Economic Coordination, where he worked on economic matters pertaining to the future occupation of Italy. In May 1946, he joined the United Nations Relief and Rehabilitation Administration (UNRRA).

In December 1948, Wadleigh confessed to the House of Un-American Activities Committee that from early 1936 to March 1938 he had passed State Department documents to Whittaker Chambers. In May 1949 Wadleigh gave evidence against Alger Hiss during his perjury trial. Wadleigh admitted that he was part of the same spy network as Chambers and Hiss. He did this because of "the failure of the Social Democrats in Germany to offer effective resistance against Hitler, the growing power of the Nazis in Germany and of the ruling group in Japan, and the Fascists in Italy.” Wadleigh explained that he saw “the Communists and Soviet Union” as “offering the only effective opposition.” Federal prosecutor Thomas Murphy pointed out that Wadleigh only wanted to stop the rise of fascism; "we all came to hate it, but he saw it earlier."

Julian Wadleigh died in 1994.