sentences:  A combination of tenacious Russian defense and reports of British submarines in the area—proved by the torpedoing of the battlecruiser on 19 August—caused the German navy to break off the operation.In the meantime, "Prinz Heinrich"s boiler tubes were in need of replacement, so she was detached for repairs at Kiel, where she arrived on 11 August.Repairs were completed the following month, and she arrived back in Libau on 22 September.