It apparently grew worse but at times he was completely free from symptoms. In the latter part of 1940 while playing tennis he experienced a sudden pain in his lower right back—it seemed to him that "something had slipped." He was hospitalized at the Lahey Clinic ... for ten days. A low back support was applied and he was comfortable. Since that time he has had periodic attacks of a similar nature.Kennedy's service in the southwest Pacific on PT boats —which he managed to arrange by calling on his father's connections to hide his various illnesses from military physicians—added to his pain, especially after a Japanese destroyer sank his boat, leading to a week-long physical ordeal. (For all the accuracy of the popular accounts praising Kennedy's valor on PT-109, the larger story of his endurance has not been told. Lennie Thom, his executive officer, wrote letters home discussing JFK's back problem and his refusal to report to sick bay: "Jack feigned being well." Kennedy acknowledged to his parents that life on the boats was "not exactly what the Dr ... ordered." But he did not let on to his crew or his commanding officer that he was ill or in pain. And except for his chronic back ailment, which he simply could not hide, and which he seemed to take care of by wearing a "corset-type thing" and sleeping with a plywood board under his mattress, the men on PT-109 saw no poor health. Before the war was over, however, Kennedy found himself once again in the hospital for both back and stomach problems.)