Vulcanian expedition

From Memory Alpha, the free Star Trek reference

The Vulcanian expedition was a mission in the early 23rd century. James T. Kirk served on the expedition, along with Timothy. (TOS: "Court Martial")

As Vulcanian is another word for Vulcan, it is probable this had something to do with the Vulcans, or their planet.

It can be assumed that the expedition took place between Kirk's graduation in 2256 and 2266, since Kirk mentioned having last seen Timothy then, but having not seen others since his Academy graduation.