Rubuta ci gaba don wannan sakin layi - A cikin 1916, bayan shigar Romania cikin Yaƙin Duniya na I, Rainer ya koma Bucharest kuma ya koma Marta, ana kiransa don aikin likita a matsayin colonel. A lokacin yakin basasa na 1916, Rainers sun kafa dakunan tiyata a asibitocin da suka cika da wadanda suka ji rauni daga yakin Turtucaia
da kuma harin Zeppelin a Bucharest. Daga baya, a lokacin mamayar Bucharest ta Tsakiyar Tsakiya, Francisc Rainer ya kafa asibitoci na wucin gadi a makarantu. Ya ci gaba da koyarwa a ƙarƙashin gwamnatin Jamus, don haka ɗalibansa ba za su rasa shekara ba, amma kuma an tilasta masa koyar da darussan daban don ɗaliban Jamusawa. Ya yi nasarar hana hukumomin mamayewa daga kwace dukiyar jami'ar. Ana kallon su a matsayin wadanda ake zargi da siyasa, an ware Rainers don tsare su a Bulgaria, amma an tsallake su ta hanyar shiga tsakani na Minovici a madadinsa. Marta Rainer, wacce ta gudanar da asibitocin yaƙi, ta shirya ƙungiyoyin likitocin tiyata don taimakawa wajen magance rikicin jin kai, kuma ta yi aiki ba tsayawa a lokacin hunturu mai tsananin sanyi na 1917<unk>1918.