Complex sentence: In the letter, Eisenhower told Patton he had been informed of the slapping incidents, and while he would not open a formal investigation into the matter, his criticism of Patton was sharp.
Split into simpler sentences: In the letter, Eisenhower told Patton he had been informed of the slapping incidents. He said he would not be opening a formal investigation into the matter, but his criticism of Patton was sharp.