US President George W. Bush said Wednesday that rebuilding Iraq and Afghanistan as the wars rage on is proving difficult and "we're learning as we go." The president hearkened back to the patriotic sacrifice of World War II, the deadliest conflict in history, in again suggesting the country must hold firm and not lose its nerve. "After World War II, we helped Germany and Japan build free societies and strong economies," Bush said. "These efforts took time and patience, and as a result, Germany and Japan grew in freedom and prosperity. Germany and Japan, once mortal enemies, are now allies of the United States. And people across the world have reaped the benefits." The president spoke on a day intended solely for celebration, the commencement for more than 1,000 graduates of the US Air Force Academy.