President Xi Jinping of China announced on Thursday that he would reduce the country’s military personnel by 300,000, using a speech marking 70 years since the end of World War II to present the People’s Liberation Army as a force for peace and regional stability.

The Chinese military has over two million members, and Mr. Xi has embarked on an accelerated modernization of the armed forces, which would shift spending from the traditional land forces to more advanced sea and air forces, which require fewer but better trained personnel.

But Mr. Xi described the cut as a gesture of peace at a time when China’s neighbors have grown increasingly worried about its territorial claims and military strength.

“I announce that China will reduce military personnel numbers by 300,000,” he said, immediately after declaring that the military was “loyally committed to its sacred duty of defending the security of the motherland and the peaceful life of the people, and loyally committed to the sacred duty of safeguarding world peace.”

He spoke just before the start of the parade in central Beijing.