Museums are not usually known for online trolling, so when one of the world’s great art institutions uses provocative hashtags like #Nazis and #Wehrmacht to make digital demands that Germany return a stolen painting, it is bound to draw attention.

The Uffizi Galleries in Florence, Italy, is calling on the German government to step into a dispute over a baroque painting that German soldiers took 75 years ago. “Vase of Flowers,” by the 18th-century Dutch master Jan van Huysum, is in private hands in Germany, and neither the museum nor the Italian authorities have been able to persuade or pressure the people who have it to give it up.

The Uffizi made its message public on Twitter on Tuesday, with a link to a lengthy “appeal to Germany for 2019” by its director, Eike Schmidt. It also posted on its website a video showing Mr. Schmidt ceremoniously affixing a black-and-white photo of Van Huysum’s still life in the Room of the Putti of the Pitti Palace, which is overseen by the Uffizi, where the painting hung before it was stolen during World War II.