The Koreans had nothing more than rifles and it was their choice to charge in human waves.
Nobody used human wave tactics in Korean war, Nobody used human wave tactics in WW2 also. Except for some of the Japanese commanders doing BANZAI charges.
The reason why the North Koreans and Chinese took so many casualties was because they had no artillery, no tanks, no aircraft. They had nothing but grenades, rpgs and semiautomatic rifles. They managed to push the USA forces back by discipline and tactics.
Korean War - Wikipedia, the free encyclopedia
UN aerial reconnaissance had difficulty sighting PVA units in daytime, because their march and bivouac discipline minimized aerial detection.[33]:102 The PVA marched "dark-to-dark" (19:0003:00hrs), and aerial camouflage (concealing soldiers, pack animals, and equipment) was deployed by 05:30hrs. Meanwhile, daylight advance parties scouted for the next bivouac site. During daylight activity or marching, soldiers were to remain motionless if an aircraft appeared, until it flew away;[33]:102 PVA officers might shoot security violators.[41] Such battlefield discipline allowed a three-division army to march the 286 miles (460 km) from An-tung, Manchuria to the combat zone in some 19 days. Another division night-marched a circuitous mountain route, averaging 18 miles (29 km) daily for 18 days.[41]
People's Volunteer Army - Wikipedia, the free encyclopedia
Similar to Europeans during the Mongol invasions, the popular perception believed that Chinese victories were due to simple human wave tactics. In fact, Chinese forces used rapid attacks on the flanks and rear and infiltration behind UN lines to give the appearance of vast hordes. This, of course, was augmented by the Chinese tactic of maximizing their forces for the attack, ensuring a large local numerical superiority over their opponent.[8][9] The initial Chinese victory along the Yalu River was a great morale booster for the PVA and the first Chinese victory over the West in modern times. However, by late 1951, overextended supply lines and superior UN firepower had forced a stalemate. The North Koreans that invaded in 1950 had been much better supplied and armed by the Soviets than the Chinese Army had been. The main arms of the PVA were captured Japanese and KMT arms,[10]
Historian and Korean War veteran Bevin Alexander had this to say about Chinese tactics in his book How Wars Are Won:
"The Chinese had no air power and were armed only with rifles, machineguns, hand grenades, and mortars. Against the much more heavily armed Americans, they adapted a technique they had used against the Nationalists in the Chinese civil war of 194649. The Chinese generally attacked at night and tried to close in on a small troop position generally a platoon and then attacked it with local superiority in numbers. The usual method was to infiltrate small units, from a platoon of fifty men to a company of 200, split into separate detachments. While one team cut off the escape route of the Americans, the others struck both the front and the flanks in concerted assaults. The attacks continued on all sides until the defenders were destroyed or forced to withdraw. The Chinese then crept forward to the open flank of the next platoon position, and repeated the tactics."
Roy Appleman further clarified the initial Chines tactics as:
"In the First Phase Offensive, highly skilled enemy light infantry troops had carried out the Chinese attacks, generally unaided by any weapons larger than mortars. Their attacks had demonstrated that the Chinese were well-trained disciplined fire fighters, and particularly adept at night fighting. They were masters of the art of camouflage. Their patrols were remarkably successful in locating the positions of the U.N. forces. They planned their attacks to get in the rear of these forces, cut them off from their escape and supply roads, and then send in frontal and flanking attacks to precipitate the battle. They also employed a tactic which they termed Hachi Shiki, which was a V-formation into which they allowed enemy forces to move; the sides of the V then closed around their enemy while another force moved below the mouth of the V to engage any forces attempting to relieve the trapped unit. Such were the tactics the Chinese used with great success at Onjong, Unsan, and Ch'osan, but with only partial success at Pakch'on and the Ch'ongch'on bridgehead."[11]
Historian Bruce Cumings noted that when Chinese soldiers and officers saw how Americans fought the war, they were surprised by how freely the Americans would resort to what they considered to be excessive and unnecessary force. One Chinese soldier stated that if the Americans encountered a single sniper hiding in a village or house, they would invariably call in massive artillery and air attacks, destroying the entire village and killing everyone in it. He asked, "Why do they do this instead of simply sending in soldiers to kill the sniper?" American superiority in military hardware had profound consequences for the Korean people on the peninsula as well as the soldiers fighting the war.