Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun

Looking back: Following a concerted effort by police in August 1971 to infiltrate Vancouver's recreational drug scene with undercover officers, a 'smoke-in' pro-marijuana protest rally held by the Youth International Party was attacked by police officers in what would become known as The Battle of Maple Tree Square. 79 protesters were arrested as police charged civilians on horseback and beat them with riot batons. A subsequent inquiry by a Supreme Court justice would call the incident a 'police riot'. Glenn Baglo / Vancouver Sun