The United States begins <a href="https://en.wikipedia.org/wiki/Operation_Menu" id="mwASk" rel="mw:WikiLink" title="Operation Menu">secretly bombing</a> the <a href="https://en.wikipedia.org/wiki/Sihanouk_Trail" id="mwASo" rel="mw:WikiLink" title="Sihanouk Trail">Sihanouk Trail</a> in <a href="https://en.wikipedia.org/wiki/Cambodia" id="mwASs" rel="mw:WikiLink" title="Cambodia">Cambodia</a>, used by <a href="https://en.wikipedia.org/wiki/People's_Army_of_Vietnam" id="mwASw" rel="mw:WikiLink" title="People's Army of Vietnam">communist forces</a> to infiltrate <a href="https://en.wikipedia.org/wiki/South_Vietnam" id="mwAS0" rel="mw:WikiLink" title="South Vietnam">South Vietnam</a>.