In response to the purported downing of a Russian civilian airliner in the Sinai in Egypt, the Kremlin is now poised for a nuclear strike on sites controlled by the Islamic State. Citing its right to protect its people and interests in Russia and abroad, Intelligence officials have anonymously reported that Russia is moving its tactical nuclear units closer to its international boundaries and its frontier with other hotspots within Russia, such as the northern Caucasus region. The Russian military have been called up to help evacuate Russian nationals within these hotspots and have ordered non-essential civilians to leave Syria, Iraq, the Gulf states and other nations in the Arab world. 
Although Russia's poising to use its nuclear weapons on ISIS, Russia held a secret meeting with NATO, reassuring them that Russia has no intentions on using nuclear weapons on either Georgia or the Ukraine, citing that attacking either of them would invoke a nuclear strike from NATO. Also Russia had consulted with the Syrian government as well as the governments of its allies in the region, who in turned told the Kurds and other allied militias of a possible nuclear strike, warning them to move allied civilians from areas that might be struck by Russia's nuclear weapons. 

A meeting of allied nations and Russia was held in Teheran within hours of the downing of the civilian passenger airliner in the northern Sinai- in which media reports have said that there was no in-climate reported at the time of the crash and witnesses on the ground claim a line of smoke went from the ground in the direction of the airliner before the ground to air missile hit the airliner. SITE has reported that a video purportedly made by either ISIS supporters or ISIS themselves that shows the downing of the airliner. The White House has declined to make a statement about this incident and the Kremlin's use of nuclear weapons. However, the Kremlin says the use of nuclear weapons is justified to protect its citizens and its interests, namely helping to sustain the government of Bashar Al-Assad and keeping the its allies in power in Iraq and Iran, which are considered allies to Russia. Their common interest in destroying ISIS motivates them to work together. 
However, the US has stated its fears that deploying nuclear weapons near the region would spur an nuclear arms race in other nations in the region, namely Saudi Arabia and the nations within the Gulf Cooperation Council, a group of Sunni Muslim nations located in the Persian Gulf region, which have aided in the creation of ISIS and continue to support it like the way they supported Iraqi insurgents during the Iraq War (2003-2011). Both the US and the UN are concerned that the conflict in the region could lead into a wider conflict, possibly a world war. 
(multiple intel reports concerning the downing of the Russian civilian airliner in northern Sinai, ISIS' purpoerted claim of responsibility and Russia's official response)