Lo joined the force in 1984 and has led its 30,000 uniformed officers since 2015. However the unrest that has gripped Hong Kong since June has likely been his most significant challenge to date.

His department has been accused of using excessive force to disperse unauthorized gatherings and cooperating with local gangs who oppose the demonstrations. Police deny both allegations, but say officers are emotionally and physically drained due to months of confrontation.

Protesters have been calling on Lo to resign since they stormed the city's legislature in July. However a police spokesperson said on Friday that Lo was retiring on November 18 because Hong Kong's civil servants are required to leave their posts when they reach a certain age.

"According to our notice, our commissioner of police has been granted service up to November 18th, 2019. This was announced last year. At this moment we have not received notice that this arrangement will be changed. The police have a well-established plan for succession," police public relations office Acting Chief Superintendent Kong Wing-cheung said at a media briefing on Friday.

Lo reached retirement age in November 2018, but Hong Kong leader Carrie Lam granted him a waiver last year that allowed him to stay on the job. Lam's office did not respond to CNN's email asking whether Lo would be granted another extension.

Protesters hold banners and placards including a defaced poster of Hong Kong Police Commissioner Stephen Lo as they march during the annual pro-democracy rally on July 1.

Now in their 18th week, the protests began in opposition to a bill which would have allowed extradition from Hong Kong to mainland China. They have since evolved into calls for democratic reforms and investigations to alleged police wrongdoing.
Over the summer, authorities have used live ammunition, tear gas, pepper spray, rubber bullets and water cannons to disperse demonstrators. On the front lines, protesters have targeted police with petrol bombs, iron bars, tools, bricks and lasers.

Trust in the force has eroded in parts of Hong Kong. Some citizens are considering leaving, fearing their city's future.

Protesters have also been calling for an independent investigation into alleged police brutality - with some even calling to disband the whole department.

At a background briefing in August, a senior officer said police only used force in response to violence. Authorities have also vowed to fully investigating allegations of misconduct, including a July incident in which officers were accused of looking the other way as a mob bashed demonstrators and passers-by.

Hong Kong Chief Secretary Matthew Cheung said Thursday that more than 2,300 people had been arrested during the unrest - 750 of whom are under 18.

Lam's attempts to mollify protesters have so far fallen flat, and protesters have responded to several of her decisions with increased violence. The city's leaders have also been accused of politicizing the police force by putting it on the front lines of a crisis playing out between the government and its critics.

At the background briefing in August, a senior police commander said the current unrest " is a political issue" and "needs a political solution to solve it."