Rav Kook spent several of the war years in London, when he was unable to return to Eretz Yisrael due to the outbreak of World War I. He temporarily accepted a position as rabbi of the Machzikei HaDath synagogue of London. His private secretary, Rabbi Shimon Glitzenstein, recorded his experiences with Rav Kook in a booklet called "Mazkir HaRav," including the following description of a sleepless night in a London bomb shelter.
During the aerial bombardment over London during the First World War, the residents of the city chose various shelters. The Jews who lived near Rav Kook took shelter in the cellar of the Machzikei HaDath synagogue. Against his will, Rav Kook would also go there, but only to alleviate the fears of his family.
The cellar was crowded and suffocating. The children wailed and the mothers complained. Some of the men gathered around Rav Kook and began reciting psalms together. As the noise and explosions increased, they stopped saying psalms. Those musically-inclined began to sing loudly in order to drown out the terrifying sounds from outside. Some people protested, but the Rav encouraged the singers to sing even more loudly.
After several hours of a long, sleepless night in the shelter, most had fallen asleep. Only Rav Kook remained calmly in his spot, without a sign of fatigue or distress. In his hand he held his small Tanach (Bible). He recited chapter 43 of Psalms, which opens with the request:
|"Judge me, God, and fight on my behalf against a merciless nation."|
I was accustomed to the Rav's recital of psalms when he was alone in his room. He would say them loudly, with bitter weeping and an outpouring of the soul. This recital of psalms, however, was different. I did not listen to the words, which were recited quietly, but to the unique melody which accompanied them. The tune was full of soul; it was permeated with a spiritual sweetness.
From the depth of his soul, Rav Kook poured forth his petitions before his Father in heaven. It was as if, through his voice, the entire Jewish nation was pleading for compassion:
|"Send Your light and Your truth; they will guide me. They will bring me to Your holy mountain and to Your dwelling place" (Ps. 43:3).|
The Rav was completely focused on his recitation. Even when it was announced that the danger had passed, he remained oblivious to the commotion of those gathered there, and continued reciting the psalm to the end.
(Adapted from Shivchei HaRe'iyah by Prof. Chaim Lifshitz, pp. 129-130.)
 The first ever aerial bombardment of civilians took place on January 19, 1915, when German Zeppelins dropped 24 high-explosive bombs over several English towns. Over the next three years, the Germans dropped 5,800 bombs over England, killing 557 people and injuring 1,358. (Wikipedia, 'Aerial bombing of cities.')