A shekara ta 1644, Mercy ta yi adawa da sojojin Faransa, yanzu a ƙarƙashin Great Condé da Vicomte de Turenne. Ya kama Freiburg kuma daga bisani ya riƙe shi a cikin yakin basasa amma mai zub da jini a watan Agusta. A ranar 2 ga Mayu, 1645, ya ci Turenne a Mergentheim. Daga baya a cikin 1645, sake yin yaƙi da Condé da Turenne, an kashe Mercy ta hanyar bindiga a cikin
Yaƙin Nördlingen (ko Allerheim) a ranar 3 ga watan Agusta yayin da yake jagorantar ƙarfafawa zuwa aikin aikin. A wurin da ya fadi, an kafa dutsen tunawa da rubutun "Sta viator, heroem calcas", wanda ake zargin umarnin Condé. Da farko an kawo gawarsa zuwa Donauwörth a kan motar bindiga sannan kuma zuwa Ingolstadt washegari, inda aka binne shi a cikin Cocin Saint Maurice. Faransanci Marshal Gramont, wanda aka kama a yakin, ya ba da rahoto game da maraba da jinƙai da Mercy ta samu daga mutanen garin da suka hanzarta zuwa ƙofofin. Ya shahara sosai kuma ana girmama shi sosai a Ingolstadt, inda ya kasance kwamandan sansanin soja da gwamna.