Complex sentence: According to Linus Pauling, Einstein later regretted signing the letter because it led to the development and use of the atomic bomb against civilian populations, adding that Einstein had justified his decision because of the greater danger that Nazi Germany would develop the bomb first.
Split into simpler sentences: According to Linus Pauling, Einstein later regretted signing the letter because it led to the development and use of the atomic bomb against civilian populations. Einstein justified his decision because of the greater danger that Nazi Germany would develop the bomb first.