On Friday 6 May 2011, 
during the 2011 Syrian uprising or civil war, Syrian government armed forces with tanks and troops started an attack on and occupation of Homs, Syria's third largest city with 650,000 inhabitants. 
Until 12 May they reportedly killed 37 residents and cut off water and medical care, held house-to-house raids to arrest hundreds of residents and shelled the town.
On 13, 20, 21, 27 and 29 May, again 21 protesters reportedly were killed by security forces. At least 13 soldiers or policemen were killed in May by terrorist groups, the government reported.
Background.
15 and 16 March 2011, demonstrations for democracy took place in six cities across Syria, the largest protest was in Daraa. 
This started a series of ever larger and angrier demonstrations all around Syria through March and April, with security forces firing on demonstrators resulting in hundreds of deaths. 
The protests spread, among other places, to Homs on Friday 18 March, after online calls for a "Friday of Dignity" (). 2,000 protesters then took to the streets in Homs after Friday prayers.
As protests in Syria continued, Homs became one of the most restive cities in Syria, 
with more protests on 25 and 29 March and 95 civilian deaths during protests on 1, 8, 17–19, 22 and 29 April 2011.
On 25 April, the Syrian government had intensified its crackdown on the protests with an organised military attack on the city of Daraa, on 26 April on Douma.
Timeline.
On 6 May 2011, Homs became, after Daraa on 25 April, the second centre of the Syrian protests and uprising to be confronted with a large scale, organised, deadly attack by the Syrian military.
”Armed terrorist groups” attacked a military checkpoint killing five soldiers and policemen; in chasing those groups and clashing with them another six soldiers were killed, government and military sources said.
State media reported that an “armed terrorist group” attacked a bus in Homs, killing 10 people and wounding three. Some soldiers(s) and officer(s) were killed by “armed terrorist groups”, the military said.
Tanks were dispersed and security check-points set up at the entrance to each suburb, searching anyone passing through, a residential doctor in Homs said; health centers and a school were transformed into command centers for security forces, he said.
Activists reported nine people killed in Bab Amr and nearby villages and dozens wounded. Between 4 and 11 May, 500 people were arrested in Homs, according to activists. State news agency SANA reported troops having “arrested dozens of wanted men and seized large quantities of weapons and ammonition” in Bab Amr.
Aftermath.
This May 2011 operation did not quell protests in Homs, nor subdue the city: October–November 2011, rebels in Homs’ Baba Amr neighbourhood ambushed government's security forces. 
More uprising and warlike events occurred until May 2014 in Homs, after July 2012 all unmistakably events of the Syrian Civil War that by then undisputedly was taking place in Syria.
References.
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