Homeland Security agents worked with local police agencies to arrest 23 alleged gang members and their associates, mostly in Fresno and Sanger.
The main target is Surenos, a gang with Mexican mafia connections, and one that's recently established a major presence in the Central Valley.
X marks the spot in Southwest Fresno's back alleys. Gang wars playing out on the streets, announced by graffiti.
"X3 signifies 13 which is the number associated with Surenos," said Mike Prado, resident agent in charge for Homeland Security Investigations Fresno, as he stood next to one example of graffiti.
The gang of the south is creeping north, according to federal agents, and marking its territory in areas formerly controlled -- and graffitied -- by Bulldogs and Nortenos.
"They decay neighborhoods from the inside out," Prado said. "They make it unsafe in a lot of areas for kids to go out and play."
Homeland Security investigators took note and took action.
In Fresno, in Sanger, and the rest of the Valley, they went into Sureno strongholds and looked for reasons to make arrests.
"So I'm being arrested for a warrant?" said one alleged Sureno as police led him, in handcuffs, to the back of a patrol car.
A warrant for destruction of property got him locked up. And similar scenes played out across the country.
The Department of Justice says Sureno membership is expanding faster than any other gang in the country.
Murder, extortion, and drugs are their currency. Project Southbound is the response -- the largest operation of its kind by Homeland Security.
Federal agents arrested more than 600 people with Sureno ties. Most of them now face criminal charges. The rest are being deported.
If nothing else, the gang is on alert that police are watching them.
"The Surenos are a significant criminal organization," Prado said. "They're a transnational gang that's a priority of HSI and law enforcement in general."
The Surenos originally formed in southern California, but they've spread all across the country. The arrests in this operation came in 179 different cities, as far northeast as New York.