The cenotaph that stands outside Old City Hall has been vandalized with spray paint.
Toronto police are at the site, at Bay Street and Queen Street West, on Tuesday morning to investigate.
Const. Alex Li said someone alerted police at 7 a.m. By noon, city crews had started the work of pressure-washing the graffiti off of the historic structure.
Blue spray paint reading "ye broke faith" in capital letters was scrawled on the base of the monument. On the back of the cenotaph, there is more spray paint that reads "with us."
Mayor John Tory called the act "disgraceful" and "unacceptable," especially because of the timing of the incident.
"There's never any excuse for this kind of vandalism," he said.
Premier Doug Ford tweeted about the incident and said he hopes police will find the person responsible.
"Disgusting to see a monument to our heroic veterans disrespected by this shameful act of vandalism," he wrote.
While it's unclear who vandalized the memorial, it's possible the message references the well-known John McCrae poem In Flanders Fields.
"If ye break faith with us who die, we shall not sleep, though poppies grow in Flanders fields," the poem reads.
The vandalism comes just a day after the site hosted one of Toronto's largest Remembrance Day ceremonies.