A video offering a rare look at the two Al Qaeda-linked rebel groups operating in Syria offers some of the most compelling evidence yet of the involvement of western citizens in the country's ongoing civil war - and raises fears over the threat posed by these radicalized Muslims towards western countries "the day after" the conflict.
Vice News has released footage of Westerners who have joined with Jabhat Al Nusra and the Islamic State of Iraq and al-Shams (ISIS) to fight for Islamic rule - not only over Syria, but over Western countries.
"I say to the United States that your time will come," says one of the men, who gives his age as 26, "and we will bleed you to death and, Inshallah [with the help of God], shall raise a flag in the White House."
Other fighters declared that new Caliphate will "pave the way to Al-Aqsa" through Syria, confirming fears in Israel that Islamist rebels plan to turn on the Jewish state in the event they succeed in overthrowing Syrian President Bashar al-Assad.
One British national declares that the UK has decided to side with the "enemies" of the Syrian people - which he identifies as the US and Iran, leaving Sunni Muslims "no choice" but to fight in Syria, "Palestine". And he warns that Britain is next.
The channel also notes that about 10% of Syrian rebels are foreign nationals - and that after the consolidation of rebel forces, that number will only continue to grow.
Just last week, BBC reported that hundreds of British citizens have left to fight in the bloody conflict.
The video comes as Islamist rebels in northern Syria - where the video was allegedly taken - have suffered a series of setbacks, both at the hands of regime forces and against independent Kurdish militias, who oppose both the Assad regime and predominantly-Arab rebel movement.