The fortress of Leerort and the Dieler Schanze were important Early Modern fortifications in the county of East Frisia and bear witness to the political and social balance of power in the region. However, they also reflect the conflicts that the young county had with outside parties. While the historical context of both fortresses has already been outlined several times, archaeological excavations have only recently taken place. As part of the INTERREG IVa-funded project "Grenzland Festungsland", the "Ostfriesische Landschaft" association of municipalities investigated both fortifications in 2010-13. The study of historical sources, extensive geophysical prospection, a LiDAR survey, targeted minimally invasive excavations, and the evaluation of finds have