During the Cold War, the US and USSR were fighting in proxy wars and aiding both sides with weapons and funding. Post Space Race, Chinese border skirmishes during the 1980's had both superpowers on high alert, the NATO and Soviet blocs were prepared to declare war on China after rogue Chinese aircraft were seen over Mongolia and Kazakhstan. The jets were ordered to leave Soviet airspace. After landing in China, the pilots were stripped of their rank and put on trial for treason. With the dawn of the 21st century, terrorism in the Middle East, Europe, United States and former USSR has become a concern, with suicide bombers attacking the Moscow and London subways in 2004 and 2007.