Karate didn't invent Breaking/Tameshiwari, Korea had it first. Quoting Graham Noble who has a lot of reputable sources & references in this issue: "Breaking objects with the hands and feet has probably existed in the eastern martial arts for hundreds of years. In Japan it certainly predated the introduction of karate in the 1920s. William Bankier, the strongman "Apollo", wrote about the edge of the hand blow in his 1905 book "Jiu-Jitsu. What It Really Is", adding that "Some of the Japs who made a study of this sort of thing have been known to actually break very large stones with their bare hand. To such an extent had these men developed the heel or side part of the hand that it almost became as hard as stone." During his military service in France in World War 1, Bob Hoffman, the founder of "Strength and Health" magazine saw an example of breaking in Paris, of all places: "In France during the war, Bob Hoffman told me that he saw a Japanese sidewalk performer actually break slabs of marble with chop blows of his hand. The side of his hand was about half an inch thicker than a normal hand". In 1940 the "Japanese American Courier" reported that "Marking its 34th anniversary the Tacoma (judo) dojo will hold its annual tournament Sunday afternoon at the Buddhist Church auditorium . . . Over 40 black belts are listed for action. An additional feature on the programme will be Masato Tamura's 'rock breaking' demonstration via the ancient Japanese art of "kiai jutsu". He will also oppose a quintet of picked black belts". Tamura was a well known judoka who had got his third dan during Jigoro Kano's visit to America in 1938. In none of these accounts, incidentally, is there any mention of karate." Mas Oyama in America, by Graham Noble 400 years ago, there were many history books all recording the same event of Korean Hand Breaking a large stone as big as a Soban table. https://i.imgur.com/d3vM6SR.png In 1692's Korea, Ikmyung Yang was also recorded to break stone by hand strike using Yongryuk. It also mentioned that Breaking/Tameshiwari is a set of games with similar nature. https://i.imgur.com/yJFsJWN.png Yong means stacking speed & power. Korean strike techniques also showed shoulder-push for hand strike. Mas Oyama introduced Breaking/Tameshiwari to the modern curriculum of Karate; Mas Oyama added this shoulder-push & Yong speed to Karate's Tameshiwari/Breaking. It's not from boxing cause Mas Oyama was a Korean who was familiar with Korean techniques. Also, Kiaijutsu (Korean Kihapsul/Charyuk is pronounced like that in Japanese) was popular in Japan at the era. In 1934's Korea, a reputable newspaper also recorded Korean Kihapsul breaking Yeonwa (soft shingles, roof tiles) with fist. It also mentioned Taoist Yoga (chejo). https://i.imgur.com/UqPLaLW.png To summarize, Karate didn't invent Breaking/Tameshiwari. They got it from Korean Kiaijutsu & Korean Mas Oyama (Choi). They also adopted shoulder-push & Yong speed for hard frontal strike from Korea.