On July 11, 2021, about 1000 eastern daylight time, a Cessna 172, N5340R, was substantially damaged when it was involved in an accident near Eagle Butte, South Dakota. The pilot was uninjured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The pilot reported that, about 6 miles from Cheyenne Eagle Butte Airport (84D), he noticed that the engine’s oil temperature was high, and he heard a “clattering noise.” He reduced the engine power by about 100 rpm and diverted to 84D. About 2 miles from the airport, the engine lost all power. Unable to reach the runway, he performed a forced landing to a wheat field. During touchdown, the nose wheel impacted rising terrain, the airplane bounced, the nose gear separated, and the airplane nosed over, coming to rest inverted. The airplane sustained substantial damage to the left lift strut and fuselage. Examination revealed a large hole in the top of the engine case adjacent to the No. 6 cylinder. The cylinder and connecting rod were removed and sent for examination at the NTSB laboratory in Washington, DC. The examination of the connecting rod revealed fatigue cracking in multiple locations along the outer surface at the transition from the neck to the crankshaft bore. The fatigue crack propagated about halfway through the connecting rod cross section before the remainder fractured from overstress. The fatigue initiation sites were collocated with deep grinding marks.