Oradour-Sur Glane

Limoges is the closest town serviced by rail from Paris - about 3+15 hrs from Austerlitz. Can check schedules on the SNCF website https://www.sncf.com/en.
From there it's about a 25 minute drive to Oradour-Sur-Glane.
Believe there are also several buses per day from Limoges to the newer town of Oradour, which is a short walk from the site of the massacre, but a car would provide more flexibility.

We visited Oradour-sur Glane on a tour. Our route was from Chinon to Sarlat with a stop at Oradour. I would agree that Limoges may be your best overnight base. Oradour is a 20-30 minute drive per car. Well worth the visit. As a side note- we were there in Sept. 2013. The day before our visit, French President Francois Hollande and Germany's Joachim Gauck paid an historic visit to the ghost village of Oradour-sur Glane . Glauck was the first German leader to visit the site. They were accompanied by two of the three living survivors, including 88 year old Robert Hebras. The three men walked in silence hand in hand.

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I spent several nights in Limoges in 2019 and took a day trip to Oradour-sur-Glane via bus. There's no rail service to Oradour. The museum-like visitor center was very well done; I spent more time there than I had expected and ended up having to rush through the memorial site itself due to the bus schedule, so I'd caution you to allow enough time.

Limoges is worth a visit on its own. It has a sizable, picturesque historic center and some really good museums of decorative arts. Visiting the porcelain museum is like taking a course in the subject: They loan you a tablet loaded with voluminous information on the history of porcelain.

It's funny to see this post on a day when I'm planning a similar visit. We will hopefully being visiting in late September. We are doing it between Amboise and Bordeaux. We are taking the train from Amboise to Limoges and spending two nights there. At this point, I am going to use a cab to see Oradour-Sur Glane from Limoges. If I find another way to get out there (buses don't seem to be frequent enough), I will come back and post again.

I can't help with how to get there because I had a car and stopped between two other destinations. I will say, however, that it is so worth any kind of inconvenience to get there if you are at all interested in WWII history and the German occupation of France. This site was the most moving experience I've had at any WWII memorial, including the D-Day beaches, Auschwitz, and Dachau. I was absolutely stunned when I got there even though I knew the story before I went there. I had expected to be moved by Auschwitz mostly because of the horrible scope of the atrocities committed there, but this was an eye-opener for me.