During the Second World War, Matthews served as a Director and Vice President of the United Service Organizations (USO) and was also involved in war-relief work.

A lawyer and banker by background, Matthews had worked closely with SECDEF Johnson on political fundraising for Truman during the 1948 presidential campaign.

In order to fund his postwar domestic spending agenda, Truman had advocated a policy of defense program cuts for the armed forces at the end of the war, and the Republican Party majority in the Congress, anxious to enact numerous tax cuts, approved of Truman's plan to "hold the line" on defense spending.

In addition, Truman's previous experience in the Senate during World War II had left him with lingering suspicions that large sums had been, and were continuing to be, wasted in the Pentagon.

In the restrictive defense funding environment following World War II demobilization, this focus on the B-36 would be at the expense of aircraft carriers and Naval Aviation, as well as the Marine Corps and its amphibious assault role which Truman, Johnson and Matthews all saw as obsolete.

[4] Top Navy and Marine Corps leaders publicly expressed their dissatisfaction with the Defense Department's plans and policies in this regard, and several senior admirals, including the Navy's top admiral, ADM Louis E. Denfeld, the Chief of Naval Operations (CNO), were forced by Matthews to resign and retire, or did so in protest.

All of the U.S. armed forces were under major strain as they simultaneously tried to meet the demands of a hot war in Asia and an intensive defense build-up in support of NATO in Western Europe.

But by September 1950, with the Korean War in full swing, the fiscal situation with respect to defense spending had totally reversed and the need for robust conventional forces had become readily apparent.

[7] As a protégé of SECDEF Johnson, Matthews was similarly perceived as a liability in a now radically changed budgetary and national defense environment.

Under political pressure from the Truman administration, Matthews also resigned as Secretary of the Navy in July 1951 to become Ambassador to Ireland, the home of his ancestors.

[14] But these few successes pale when compared to Matthews' lack of advocacy for both the Navy and Marine Corps in terms of roles and missions that he had sworn an oath as SECNAV to support, and it is this failure that has driven the vast majority of derision to his legacy.

Due to Matthews' actions and inactions, the bitterness between the Navy and the Marine Corps versus the Air Force and the Army would fester and take many years to recede.

Indeed, as late as the early 21st century, there remain many retired Navy and Marine Corps officers who resent the way their services were treated by the Army and the Air Force in the late 1940s and early 1950s, combined with Matthews' systemic failure to counter it, and it has remained a touchstone in the professional education of subsequent generations of commissioned officers in the Navy and Marine Corps, especially those in Naval Aviation, in the decades since.