Much like the citizens of Konohagakure follow Senju Hashirama's Will of Fire, the shinobi of Iwagakure follow the Shodai Tsuchikage's Will of Stone. But while the Will of Fire encourages love and peace, the Will of Stone is a philosophy that seems much more fitting for the typical shinobi, advocating individual strength of body and mind and a determination to be unmovable from one's chosen path. This philosophy can cause ninja of other villages to consider Iwa shinobi to have a 'heart of stone' when they seem to care more about a successful mission or campaign than their comrades. Iwa shinobi may also be regarded as hard headed, as they tend to stubbornly resist any opposition, refuse to negotiate until they have no choice, and avoid straying from a plan in motion. But, whether uncaring and mulish or determined and unyielding, generations of strong Iwagakure shinobi have been shaped by the Will of Stone.
The largest threat the Will of Stone ever faced was the Yellow Flash. Many of his enemies feared or hated him because of his power or because of the actions he took during the Third War. The people of Iwagakure, however, had a slightly different reason. Minato Namikaze was the embodiment of the Will of Fire, and when Onoki was forced to order his shinobi to flee the Yellow Flash on sight, it was like admitting that the Will of Fire was stronger. Having your way of life defeated is the harshest loss possible.
More recently, however, the philosophy has undergone a shift. While the concepts of strength and determination still largely dominate the Iwa mindset, the shinobi that fought in the Fourth War came to realize that the Wills of Stone and Fire weren't as incompatible as they had trained themselves to believe. If one's goal is to protect their precious people, and nothing and no one can move them from that chosen path, are they not following a form of the Will of Stone? Uzumaki Naruto clearly follows the Will of Fire, yet his personal nindo sounded oddly familiar to the shinobi of Iwagakure. While Iwa still emphasizes individual abilities instead of synergy, they have since begun to accept that their dedication can be directed towards less concrete objectives.