Cleveland, Ohio: Stepping up for a job he's toyed with since the 1980s, New York developer and reality TV star Donald Trump has accepted the Republican Party's presidential nomination with a dark speech that parsed the US and the world as mean, chaotic and dangerous for Americans – whose government had failed to defend and protect them.

Trump offered himself as a can-do executive full of solutions, stating as fact but offering no detail that as president he would resolve the serial crises that "threaten our very way of life".

"I have a message for all of you," he told the closing session of the GOP convention. "The crime and violence that today afflicts our nation will soon – and I mean very soon – come to an end."

After his inauguration next January, he said, "safety will be restored". Reaching back decades to the ominous tenor of Richard Nixon's successful law-and-order electoral pitch in 1968, Trump's harsh prescriptions for dealing with crime, immigration and hostile nations amounted to a gamble that voters will embrace his sense of coast-to-coast danger and his offer to fix it for them.

Briefing reporters later, his advisers acknowledged that in bundling illegal immigrants and lawless Americans on one hand, with Syrian refugees and the so-called Islamic State on the other, as equally dangerous threats to national security, Trump was attempting to address a perceived problem in his campaign – he believed entwining the issues could win undecided voters who were anxious over recent police killings but at the same time were unsure of his ability to measure up as a commander-in-chief.

The rationale seemed to be this: if they could see Trump as a local cop, then perhaps they might also be able to see him as a global enforcer; and just as Nixon sought out the "silent majority", Trump has his eye on "forgotten men and women" who are ignored by a rigged political system that is controlled by "censors" and "cynics".

It made sense for Nixon and, later, for Ronald Reagan – but decades later analysts say that the white, mostly working-class voters that came out for Nixon and Reagan have been diluted significantly as a portion of the electorate by demographic change.

Against a backdrop of US flags and with his surname in huge gold letters on a jumbotron, Trump gave a dystopian account of modern America.

"Our convention occurs at a moment of crisis for our nation – the attacks on our police, and the terrorism in our cities, threaten our very way of life. Any politician who does not grasp this danger is not fit to lead our country," he intoned.

"Beginning on January 20, 2017, safety will be restored … I have joined the political arena so that the powerful can no longer beat up on people who can no longer defend themselves. The time for action has come."

With little regard for the practice of the last four two-term presidents to give voters a hopeful, uplifting message, Trump maintained his focus on violence and crime, illegal immigration and jobs and trade as burdens too great for Americans to bear. They had been abandoned by their government and treated with disrespect by other countries.

Starting in presidential fashion, Trump initially followed the teleprompter script, but drifted from time to time to his more robust rally style of delivery, veering from wartime gravity to rabble-rousing.

He promised to "defeat the barbarians of ISIS" and to knock into line countries that didn't respect the US – including Iran, China and any country that figured the US would protect it without being paid.

"It is time to show the whole world that America is back - bigger, and better and stronger than ever before," Trump said.

He would end multilateral trade deals and limit US involvement in global crises.

Singling out families that were victims of crime, the poor and the poorly educated, and those who had lost jobs as industry moved offshore, Trump declared: "These are the forgotten men and women of our country. People who work hard but no longer have a voice - I am your voice."

Implicitly, he rebuked president George W. Bush, arguing that 15 years of war in the Middle East had cost trillions of dollars and thousands of lives, but had made the region worse – and he then promptly blamed that all on Hillary Clinton, his Democratic challenger for the presidency.

And the night would not have been complete without the vivisection of Clinton and Obama, of whom he said: "America is far less safe - and the world is far less stable - than when Obama made the decision to put Hillary Clinton in charge of America's foreign policy.

"[Americans have] lived through one international humiliation after another" under President Obama: its sailors "forced to their knees" by Iranian captors in January; the destruction of the American consulate in Benghazi, Libya; and Obama's decision not to defend his "red line" on Syria.

Roping in Clinton, Trump charged: "This is the legacy of Hillary Clinton: death, destruction, terrorism, and weakness."

Thursday was a night when GOP convention organisers got their act together – none of the speakers and none of the delegates misbehaved and there were no technical glitches – though the fact-checkers were at work even before he had finished:

• Trump's claim that police killings were up by 50 per cent was wrong – the year-on-year number is steady;
• He cited "180,000 illegal immigrants with criminal records . . . roaming free to threaten peaceful citizens", without mentioning that most had been charged with non-violent crimes;
• He overstated unemployment among young African-Americans by almost 100 per cent;
• Neither Clinton nor Obama started the revolutions in Libya, Syria and Egypt - that was the Arab Spring;
• Hillary Clinton has not proposed abolition of the Second Amendment under which Americans have the right to go armed.

And so on. His speech – which lasted an hour and 16 minutes – was not that of a typical Republican. There was little that might sway women, Hispanics and African-Americans to pull the lever for Trump. But even he seemed surprised, stopping to acknowledge how "nice" it was to hear a Republican audience cheering his condemnation of the June massacre at a gay Latino nightspot in Orlando, Florida.

And at the end of the speech he had to rattle off a string of GOP sacred cows that had not been included in a version of the speech released just hours before delivery – these included destroying Obamacare and protecting gun rights.

He was repeatedly interrupted by chants that dovetailed with whatever point he was making – "Lock her up!" at mentions of Clinton; and "build the wall, build the wall" while talking about illegal migrants.

His self-portrait was different to that usually on offer at election time in the US – he would be a strongman, something of an autocrat who would get things done, he seemed to be saying, without all that nonsense of working with Congress.

"Nobody knows the system better than me," he said, "which is why I alone can fix it."

And still bridling at not being taken seriously, he issued a warning to the disbelievers. "Remember," he said, "All of the people telling you, you can't have the country you want, are the same people ... that said Trump doesn't have a chance of being here tonight ... Oh we love to defeat those people, don't we?"

The need for unity was addressed; its absence was not acknowledged. Trump did not mention the convention upstart, Texas senator Ted Cruz, who on Wednesday provoked a backlash when he refused to endorse Trump.

But there was a lingering suspicion that Trump had Cruz in mind when the music to close out the event, selected from Trump's personal list, included the Rolling Stones' "You Can't Always Get What You Want".