hard nut to crack

“It’s a very hard nut to crack. The Russians could spend many months and much effort storming Lysychansk,” military analyst Oleh Zhdanov told the AP.

“Bob is reclusive and quiet and a hard nut to crack,” Pullman said.

Voice control is a hard nut to crack.

“This place is a hard nut to crack,” Newgarden said.

Ukraine has proved a hard nut to crack, and the reaction of Western countries, particularly Germany, has been far fiercer than he thought.