CLEVELAND -- Donald Trump "humbly" accepted the Republican nomination for president on Thursday night, capping an historic and unlikely run to become the party's standard-bearer.Trump's acceptance speech was well within his rhetorical repertoire, themed not on a promise of morning in America or on the prospects for a better world, but on a country gripped by violence in its streets and a relentless threat of terrorism from a specific type of foreigner. Rattling off anecdotes of killings from Chicago to the country's southern border, from Missouri to France, Trump promised an end to the nation's apparent chaos should he assume its highest office.Things need to change "right now," he charged, to a roar in the convention hall. "We will be a country of generosity and warmth, but we will also be a country of law and order," he said. "Our convention occurs at a moment of crisis for our nation.""Americans watching this address tonight have seen the images of violence in the streets," he added. "Beginning on January 20th, 2017, safety will be restored."On the international stage, Trump said the American people have been repeatedly humiliated throughout seven years of the Obama administration– and laid blame for the world's challenges at the feat of his former secretary of state, Hillary Rodham Clinton, his Democratic rival."We all remember the images of sailors being forced to their knees by Iranian captors at gunpoint," he said, arguing that the nuclear deal reached last year "gave us absolutely nothing" and will "go down in history as one of the worst deals ever negotiated."He also lamented the president's infamous red line on the use of chemical weapons in Syria– "the whole world knew it meant absolutely nothing," he said– and accused Clinton of navigating US foreign policy to a dangerous place."Iran is on the path to nuclear weapons, Syria is engulfed in a civil war and a refugee crisis now threatens the West," he said. "The situation is worse than it has ever been before. This is the legacy of Hillary Clinton: Death, destruction, terrorism and weakness."Trump charged he would swiftly defeat the "barbarians of ISIS," and in a unique moment for the party, vowed to protect gays and lesbians from discrimination– at least by violent extremists."As a Republican, it is so nice to hear you cheering for what I just said," he said off teleprompter, after receiving applause for the line.Trump spent a substantial portion of his speech on immigration– his signature issue– declining to repeat his vow to ban all Muslims from entering the US. Instead, he narrowed his call to a temporary suspension of immigration from nations "compromised" by terrorism. He did not specifically name countries, but he criticized Clinton for supporting an increased intake of Syrian refugees.Trump also promised to work with America's "closest ally" in the Middle East, Israel, in a brief and passing reference.But at the close of the four-day convention here in Ohio, the candidate failed to meaningfully unite the GOP, with his chief rival from the primary campaign, Senator Ted Cruz of Texas, refusing to endorse him and encouraging Republicans to "vote their conscience."A rare protest on the event floor on Monday called for a roll call vote on the convention rules. The sitting Republican governor of the state hosting the convention was a no-show. And efforts to present Trump's family members as his character witnesses were mired by revelations that a section of his wife's speech contained plagiarized material.While Trump was successful in systematizing his campaign message– the Republican National Committee adopted his isolationist positions in its official party platform– he is unlikely to benefit from the optics of the week, which highlighted seething fissures in the party's ranks during a phase of the campaign when nominees can typically expect a bump in the polls."Don't stay home in November," Cruz told the convention hall on Wednesday night, with Trump present. "Stand and speak and vote your conscience."The Texas senator received loud boos from pro-Trump delegates, and the seeds of discord were watered by Hillary Clinton, the presumptive Democratic presidential nominee, who promptly took to Twitter to echo Cruz' message.Cruz clarified on Thursday that he would not be voting for Clinton.In conversation with the Post, party delegates across the GOP spectrum seem to have rallied behind the institution of the Republican Party, alongside Reince Priebus, its chair, and Paul Ryan, the speaker of the House."The rules are the rules, and we respected them," said one delegate, Toni Anne Dashiell, who serves as a national committeewoman for Texas.But intra-party quarrels undoubtedly put a damper on the convention throughout the week. The tone here is less enthusiastic than it is conflicted, although Trump certainly has his supporters: 'Make America Great Again!' has become a rallying cry in the hall, and Republican loyalists are equally motivated to prevent another Clinton presidency as they are to elect him, if not more so.Trump doubled down on defining his campaign by another slogan, 'America First,' in an interview with the New York Times on Wednesday, despite concerns within the Jewish community over its historic connotations.The slogan is not meant to evoke an isolationist movement from the 1940s of the same name, he said. The America First Committee, founded by Charles Lindbergh, campaigned to keep the US out of World War II. Lindbergh accused American Jews at the time of conspiring to lead the country into war."To me, ‘America First’ is a brand-new, modern term," Trump said "I never related it to the past."That theme– which underlined his Thursday night keynote address– is a stunning departure from Republican foreign policy orthodoxy of the past four decades, which defined American leadership in the world as muscular engagement furthering liberal democratic values.Trump made no apologies for the dramatic shift, however. He questioned the worth of stationing American troops abroad and threatened not to meet as president American defense commitments to its partners in NATO, an alliance which he has previously disparaged."We are going to take care of this country first," he told the Times, "before we worry about everyone else in the world."