The spillover of the Syrian Civil War is the impact of the Syrian Civil War in the Arab world and beyond. Since the first protests during the Arab Spring, the increasingly violent Syrian Civil War has been both a proxy war for the major Middle Eastern powers, Turkey and Iran, and a potential launching point for a wider regional war. Fears of the latter were realized when the Islamic State of Iraq and the Levant (ISIL), a Salafi Jihadist militant group and alleged former al-Qaeda affiliate, established itself in Syria in 2013, and later combined with the War in Iraq (2013–2017) into a single conflict the following year.
Iraq
Iraqi–Syrian border incidents
The Akashat ambush was a well planned assault against a Syrian Army convoy defended by Iraqi soldiers that took place on 4 March 2013, as the group was travelling in the province of Anbar, next to the border with Syria. The Islamic State of Iraq claimed responsibility for the ambush on 11 March. 51 Syrian soldiers were killed in the clashes.
In March 2013, a source from Sinjar hospital said that Free Syrian Army attacked Iraqi soldiers after entering Iraqi territories. This led to greater fighting throughout the country, Operation al-Shabah in May 2013 in which the Iraqi Army failed to wipe these militias out and the consolidation of several of them with ISIL. Armed conflict broke out in Al Anbar Governorate in late 2013 and by January 2014, Islamic State had mutated and grown into a massive pseudo country which has taken over much of Iraq and Syria and erased the border between the two countries in a new, multinational war. In June 2014 ISIL launched an offensive in northern Iraq taking large swaths of the country and threatening Baghdad itself, thus turning the conflict into a full-scale war that lasted until 2017.
In June 2016, the Syrian Free Army, backed by the United States, overtook ISIL forces in the border town of al-Bukamal. The city is essential to a key route linking eastern Syria to Iraq. However, in the hours following ISIL launched a counteroffensive and retook al-Bukamal, with the Syrian Free Army suffering significant casualties.
As of May 10, 2017, ISIL has maintained control over al-Bukamal and the key route linking Syria and Iraq. ISIL has additionally conducted attacks near the Waled-Tanif Border Crossing to the south, and west of Mosul in the north. The significant territorial control ISIL maintains surrounding al-Bukamal allows for relatively easy passage between the two nations.
Lebanon
The Syrian Civil War has led to incidents of sectarian violence in northern Lebanon between supporters and opponents of the Assad government, and armed clashes between Sunnis and Alawites in Tripoli. Fighting between rebels and government forces has spilled into Lebanon on several occasions. The Syrian Arab Air Force has conducted air strikes on targets in Lebanon, while rebels have launched rockets on Hezbollah targets. Fighting between supporters of the Sunni sheikh Ahmed Al-Assir, who is against Hezbollah's involvement in Syria, and the Lebanese army has killed at least 15 of its soldiers.
Lebanese–Syrian border
At the beginning of summer 2012, two Hezbollah militants were killed in a clash with Syrian rebels who were on Lebanese territory. On 17 September, Syrian Ground-attack aircraft fired three missiles over the border into Lebanese territory near Arsal. It was suggested that the jets were chasing rebels in the vicinity. The attack prompted Lebanese president Michel Sleiman to launch an investigation, whilst not publicly blaming Syria for the incident.
On 22 September 2012, a group of armed members of the Free Syrian Army attacked a border post near Arsal. This was reported to be the second incursion within a week. The group were chased off into the hills by the Lebanese Army, who detained and later released some rebels due to pressure from dignified locals. Michel Sleiman praised the actions taken by the military as maintaining Lebanon's position being "neutral from the conflicts of others". He called on border residents to "stand beside their army and assist its members." Syria has repeatedly called for an intensified crackdown on rebels that it claims are hiding in Lebanese border towns. In October 2012 Hassan Nasrallah denied Hezbollah members were fighting alongside the Syrian army, but that Lebanese in Syria were only protecting Lebanese inhabited villages from the Free Syrian Army.
In August 2014, the Syrian air force bombed the Lebanese side of the border. In December of that year, they used barrel bombs on suspected rebel installations northwest of Arsal.