Donald Trump has vowed to tackle multiple threats facing the US, in his speech in Cleveland, Ohio accepting the Republican presidential nomination.
"The crime and violence that today afflicts our nation will soon come to an end," he told the party convention.
The businessman promised his presidency would usher in a new era putting America and ordinary people first.
Mr Trump's nomination has been clouded by the refusal of major party figures like Senator Ted Cruz to endorse him.
Mr Cruz, who was his bitter rival during the primary contests, was booed off the stage by Trump supporters.
Other Trump opponents such as members of the Bush family stayed away from the convention altogether.
Mr Trump, a New York businessman who was written off when he launched his campaign a year ago, said he hoped his speech would ease tensions and unite the party.
Despite all the darkness of the opening and the rawness of Mr Trump's tone, his speech made a determined effort to expand his appeal beyond the angry white, working-class voters who make up the core of his support.
He reached out to black people - talking about their high levels of unemployment and poverty. He said the Obama administration had failed the inner cities on education, jobs and crime.
If Mr Trump's law-and-order pitch is to be successful, it cannot only be to his base - and this was a speech that acknowledged this.
In addition, Mr Trump once again went off-script when he spoke about protecting gay Americans from "violence and oppression of a hateful foreign ideology". It was a decided change in tone from a Republican nominee - and a stark contrast even from the platform his own party adopted just days