It's not in the Lincoln bio but it is in this ("Lincoln the Lawyer")-

https://books.google.com/books?id=6LRYAAAAMAAJ&q=%22President+determined+on+war+and+with+the+purpose+of+making+it+appear+that+the+South+was+the+aggressor%22&dq=%22President+determined+on+war+and+with+the+purpose+of+making+it+appear+that+the+South+was+the+aggressor%22&hl=en&sa=X&ved=0ahUKEwj2h6HJ2-XUAhVBjz4KHUR7DzQQ6AEIKDAB