When the U.S.S. President Lincoln was attacked and sunk by the German submarine U-90, on 21 May 1918, Lt. Izac was captured and held as a prisoner on board the U-90 until the return of the submarine to Germany, when he was confined in the prison camp. During his stay on the U-90 he obtained information of the movements of German submarines which was so important that he determined to escape, with a view to making this information available to the U.S. and Allied Naval authorities. In attempting to carry out this plan, he jumped through the window of a rapidly moving train at the imminent risk of death, not only from the nature of the act itself but from the fire of the armed German soldiers who were guarding him. Having been recaptured and reconfined, Lt. Izac made a second and successful attempt to escape, breaking his way through barbed-wire fences and deliberately drawing the fire of the armed guards in the hope of permitting others to escape during the confusion. He made his way through the mountains of southwestern Germany, having only raw vegetables for food, and at the end, swam the River Rhine during the night in the immediate vicinity of German sentries.
Wakati U.S.S. Rais Lincoln alishambuliwa na kuzamishwa na nyambizi ya Ujerumani U-90, na Lt. Isaac alikamatwa na kufungwa kama mfungwa kwenye U-90 hadi kurudi kwa nyambizi kwa Ujerumani, wakati alipokuwa amefungwa katika kambi ya wafungwa. Wakati wa kukaa kwake kwenye U-90, alipata habari za harakati za nyambizi za Ujerumani ambazo zilikuwa muhimu sana kwamba aliamua kutoroka, kwa lengo la kufanya habari hii ipatikane na mamlaka ya Jeshi la Wanamaji la Marekani na Washirika. Alipokuwa akijaribu kutekeleza mpango huo, aliruka kutoka kwenye dirisha la gari-moshi lililokuwa likisafiri kwa kasi, akihatarisha kifo chake, si kwa sababu ya kitendo hicho tu, bali pia kwa sababu ya risasi za askari Wajerumani waliokuwa wakimlinda. Baada ya kukamatwa na kufungwa tena, Lt. Izak alifanya jaribio la pili na la mafanikio la kutoroka, akivunja njia yake kupitia uzio wa waya wa miiba na kwa makusudi kuvutia moto wa walinzi wenye silaha kwa matumaini ya kuruhusu wengine kutoroka wakati wa machafuko. Alipitia milima ya kusini magharibi mwa Ujerumani, akiwa na mboga mbichi tu kwa chakula, na mwishowe, akaogelea Mto Rhine wakati wa usiku katika ujirani wa karibu wa walinzi wa Ujerumani.