Complex sentence: The campaign's greatest success occurred in 1999 when the Ottawa Treaty, which bans the production and use of anti-personnel mines, came into force; the United States, Russia and People's Republic of China have thus far refused to sign.
Split into simpler sentences: The campaign's greatest success occurred in 1999 when the Ottawa Treaty, which bans the production and use of anti-personnel mines, came into force. Some states, including the United States, Russia and People's Republic of China, have thus far refused to sign.