Final answer:
The precise number of USO performances through 2013 is not provided; however, the USO has a longstanding tradition of performing for U.S. troops, including during World War II with the iconic production of Oklahoma!
Step-by-step explanation:
As of 2013, the exact number of USO performances has not been specified in the information provided. However, it is known that the production of Oklahoma! played for more than a million troops in the Pacific during World War II as part of the USO tour, as the shows and performances by USO have been an integral part of boosting morale amongst U.S. troops since World War II. This illustrates the long-standing tradition of the USO providing entertainment to improve the welfare of service members. The USO has been active for many years, performing not only during World War II but also throughout the following decades up to 2013 and beyond, celebrating many other milestones and anniversaries of its establishment and operations.