Brazilian President Jair Bolsonaro has long declared war on the news media. His next target is more ambitious—history.

The right-wing former army captain, who took office in January, has made it his mission to rewrite five centuries of Brazil’s past, from colonialism to contemporary democracy.

He has denied that Portuguese colonizers were responsible for slavery here and blamed Africans instead. He has rejected that the 1964-1985 military dictatorship, which he served, was actually a dictatorship. In Israel this month, he said that the Nazis were “without doubt” leftists.

“I have the truth on my side,” Mr. Bolsonaro said in a recent television interview, explaining why he called on the armed forces last month to commemorate the anniversary of Brazil’s 1964 coup that ended democratic rule.