Original sentence: After several months trying to discover underlying patterns in PURPLE ciphertexts, an SIS team led by Friedman and Rowlett, in an extraordinary achievement, figured it out.But the best of the lot, the SIGABA — which was destined to become the US's highest-security cipher machine in World War II — was co-invented by Frank Rowlett, a young mathematician whom Friedman had been so astute as to hire.In 1941 Friedman was hospitalized with a "nervous breakdown," generally attributed to the mental strain of his work on PURPLE.Over a period of years he developed principles of analysis and discovered a number of problems common to most rotor-machine designs.While he remained in hospital, a four-man team — Abraham Sinkov and Leo Rosen from SIS, and Lt
Edited sentence: "  While he remained in hospital, a four-man team — Abraham Sinkov and Leo Rosen from SIS, and Lt.After several months trying to discover underlying patterns in PURPLE ciphertexts, an SIS team led by Rowlett, in an extraordinary achievement, figured it out.But the best of the lot, the SIGABA — which was destined to become the US's highest-security cipher machine in World War II — was invented by Frank Rowlett, a young mathematician whom Friedman had been so astute as to hire.Even so, the machine  was only constructed after Rowlett managed to overcome Friedman's hostility to the innovative concept.Friedman did subsequently, however, seek and accept recognition as the person chiefly responsible for SIGABA's creation.In 1941 Friedman was hospitalized with a "nervous breakdown.Over a period of years he discovered a number of problems common to most rotor-machine designs