For days, Hong Kong’s protesters fortified a university campus to keep police from getting in. Now, cornered by authorities, they are trying to get out.

Officers repelled one attempt Monday morning with tear gas, driving a few hundred protesters back into the Hong Kong Polytechnic campus.

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In this Sunday, Nov. 17, 2019, photo, medical volunteers help a protester retreat from the front lines of a barricade outside the Hong Kong Polytechnic University in Hong Kong. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

For days, Hong Kong’s protesters fortified a university campus to keep police from getting in. Now, cornered by authorities, they are trying to get out.

Riot police pull back after storming Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

It’s a game that has played out repeatedly during the city’s months of anti-government unrest. Protesters cause disruption, then try to melt away before police run in to grab as many as they can.

Protesters battle water cannon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Protesters battle water cannon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Office chairs burn after police try to storm the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into a university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Office chairs burn after police try to storm the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into a university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Protesters stand at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters stand at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters walk at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters walk at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters rest at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters rest at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

A protester rests at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

A protester rests at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

A hand reaches out as protesters battle water canon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

A hand reaches out as protesters battle water canon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

The protesters want to avoid arrest. The police have set up a dragnet around the campus to pick up as many as they can.

In this Sunday, Nov. 17, 2019, photo, medical volunteers help a protester retreat from the front lines of a barricade outside the Hong Kong Polytechnic University in Hong Kong. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

In this Sunday, Nov. 17, 2019, photo, medical volunteers help a protester retreat from the front lines of a barricade outside the Hong Kong Polytechnic University in Hong Kong. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

It’s a game that has played out repeatedly during the city’s months of anti-government unrest. Protesters cause disruption, then try to melt away before police run in to grab as many as they can.

Other protesters blocked a major road near Polytechnic as the work week started in a bid to help those inside the campus escape by distracting police.

Riot police pull back after storming Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Riot police pull back after storming Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Protesters battle water cannon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Protesters battle water cannon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Office chairs burn after police try to storm the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into a university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Office chairs burn after police try to storm the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into a university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

Protesters stand at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters stand at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters walk at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters walk at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters rest at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Protesters rest at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

A protester rests at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

A protester rests at Hong Kong Polytechnic University after police stormed part of the campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoVincent Yu)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

Police in riot gear move onto the Hong Kong Polytechnic University campus during the early morning hours in Hong Kong, Monday, Nov. 18, 2019. Police breached the university campus held by protesters early Monday after an all-night siege that included firing repeated barrages of tear gas and water cannons. (AP PhotoNg Han Guan)

A hand reaches out as protesters battle water canon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)

A hand reaches out as protesters battle water canon and riot police firing tear gas outside the Hong Kong Polytechnic University in Hong Kong Monday, Nov. 18, 2019. Fiery explosions were seen early Monday as Hong Kong police stormed into the university held by protesters after an all-night standoff. (AP PhotoNg Han Guan)