George Robertson has surprisingly announced he is stepping down as NATO secretary general when his four-year term ends in December. Lord Robertson have been asked by a number of governments to stay on for the optional fifth year. "I believe four years is the right term in this demanding and onerous job," Robertson said in a statement. Robertson has received widespread praise for pushing through reforms of the 19-nation alliance. Under his guidance, NATO invited seven nations to join in November and secured commitments from European allies to boost their military capabilities.