http://revach.net/article.php?id=3816

Section: Hanhagos   Category: Ma'aseh Rav
The Brisker Rov Sleeps Tight As The Bombs Rain Down
Whenever the Brisker Rov was in place fraught with danger he would search high and low to find the safest place of refuge. He would obsessively weigh the pros and cons of each place and endlessly debate what to do.  Even when he decided he was wrapped in fear of his decision.

Yet when he was trapped in Warsaw away from his home and family at the outbreak of World War II as Warsaw was being bombarded by the Nazi war machine, he did not make any issue of his place of shelter and always looked calm and went to sleep peacefully.

When asked to explain this seemingly strange behavior he said that when he is in a place of danger he has Chiyuv Min HaTorah to protect his life.  He treats this like any other mitzva and wants to make sure he fulfills his obligation in the best way possible.  The consequences of erring would mean causing his own death and he would be held responsible for it.  This was a scary undertaking.  However, he explained, right now in Warsaw there is no safe place and any possible shelter is equally dangerous.  That means that I have no responsibility to take action.  Of course I am relaxed.  It is the Kiyum HaMitzva that worries me, not the Nazi bombs.