One man had three assault rifles, extra-large magazines and a gas mask. Another had over 18 weapons, including sawed-off shotguns, AR-15s, and a grenade launcher. Earlier this year, the two might not have drawn the attention of US law enforcement. But ever since a young racist slaughtered 22 at a Texas Walmart, and another man murdered 10 in Ohio three weekends ago, the FBI has arrested at least seven right-wing extremists in what appears to be a more earnest effort to target white nationalist threats in the United States.Vaults of guns, crates of ammunitionThese are some examples of the deeply disturbing cases.On August 8, a 23-year-old Las Vegas security guard who communicated with neo-Nazis was arrested with bomb-making materials and indications he might target a synagogue or gay nightclub.A week later, a Connecticut man, 22, was detained after suggesting online that he would carry out a mass shooting. At his home, investigators found multiple hand and long guns, camouflage outfits, titanium body armor and a combat helmet.On August 12, an 18-year-old who voiced support for mass shootings was indicted for threatening to kill law enforcement officers. At his home, he had a vault full of weapons and 10,000 rounds of ammunition.Four days after that, Florida police arrested a 25-year-old man who texted his girlfriend that he was planning a mass shooting and envisioned "100 good kills." On August 17, a 20-year-old white nationalist was arrested in Ohio for threatening a Jewish community center. At his home, he had amassed multiple semi-automatic assault rifles, high-capacity magazines, and a gas mask. And this week, police in Long Beach, California, arrested a man for making a mass shooting threat, and found at his home several illegal assault rifles, thousands of rounds of ammunition, and high-capacity magazines.FBI waking upThe arrests brought to light the extent of the threat of extremist ideology on the right, and its ability to motivate uniformly young, white men into acting on their hate.They also, analysts said, mark a change after US justice authorities have been accused for years of doing little about domestic terrorism, which has now killed more Americans since 2002 than Islamist extremism."I think that federal law enforcement understand that this is at the highest level of concern," said Brian Levin, head of the Study for Hate and Extremism at California State University-San Bernardino."They are certainly devoting a decent amount of investigative resources."Analysts say President Donald Trump's refusal to attack white nationalists and neo-Nazis in the wake of several shootings and violent incidents had left the FBI reticent about fully confronting the threat.The FBI feels held back from opening investigations by Trump's refusal to criticize people he considers part of his loyal voter base, former FBI terrorism supervisor Dave Gomez told The Washington Post."It's a no-win situation for the FBI agent and his supervisor."850 domestic terror probesBut the agency has now clearly recognised the priority.FBI Director Christopher Wray said in July that they have 850 open "domestic terror" investigations and have made 100 arrests so far. The majority of those cases, he said, are "what you might call white supremacist violence." But Wray also stressed that they were targeting crimes rather than an ideology -- a sharply different approach than that for Islamic State group and Al-Qaeda sympathizers, who can be arrested for expressing support for outlawed jihadists.Wray's predecessor Andrew McCabe said Friday that the agency is overcoming that wariness, even if it could mean encroachments on civil liberties."I think the FBI appears to be refocusing, and augmenting their efforts on the domestic terrorist threat," McCabe told CNN.Now there is "a much higher degree of sensitivity... to the statements which are now seen as predictors of potentially mass shootings," he said.Levin said the arrests also show that, after the shock of recent mass shootings, the US public is more attuned to the ideological threat and ready to report any hints by perpetrators of their radical ideologies."I think that has created a familiarity among the public with what certain warning signs are," he said.