Khmer–Cham wars 
 Cham–Vietnamese wars
 Cham–Mongolian war
 Khmer–Cham wars were a series of conflicts and contests between states of the Khmer Empire and Champa, later involving Đại Việt, that lasted from the mid-10th century to the early 13th century in mainland Southeast Asia. The first conflict began in 950 AD when Khmer troops sacked the Cham principality of Kauthara. Tensions between the Khmer Empire and Champa reached a climax in the middle of the 12th century when both deployed field armies and waged devastating wars against each other. The conflicts ended after the Khmer army voluntarily retreated from occupying Champa in 1220.
 Around 950, Angkorian army under Rajendravarman II crossed the forest, pillaged the temple of Po Nagar in Kauthara and carried off the golden statue of Bhagavati in the temple, Champa's holiest deity. The invasion however ended in a "bloody defeat". In 965, the Cham King Jaya Indravaman I restored the temple and rebuilt the statue of the goddess to replace the one stolen by the Khmer. 
 In 1074, Harivarman IV became king of Champa. He had close ties to Song China and made peace with Dai Viet, but provoked a war with the Khmer Empire. In 1080, a Khmer army attacked Vijaya and other centers in northern Champa. Temples and monasteries were sacked and cultural treasures were carried off. After much chaos, Cham troops under King Harivarman were able to defeat the invaders and restore the capital and temples. Subsequently, his raiding forces penetrated Cambodia as far as Sambor and the Mekong, where they destroyed all religious sanctuaries.
 In 1127, Suryavarman II demanded Vietnamese king Lý Dương Hoán to pay tribute for the Khmer Empire, but the Vietnamese refused. Suryavarman decided to expand his territory northward into Vietnamese territory. The first attack was in 1128 when King Suryavarman led 20,000 soldiers from Savannakhet to Nghệ An, where they were routed in battle. The following year Suryavarman continued skirmishes on land and sent 700 ships to bombard the coastal areas of Đại Việt. In 1132, he persuaded Cham king Jaya Indravarman III to join forces with him to attack Đại Việt, where they briefly seized Nghệ An and pillaged the coastal districts of Thanh Hoá.
 In 1136, a Vietnamese force under Đỗ Anh Vũ counterattacked the Khmer Empire across modern-day Laos with 30,000 men, but later retreated. The Cham thereupon made peace with the Vietnamese, and when Suryavarman renewed the attack, Jaya Indravarman refused to cooperate with the Khmers. After a failed attempt to seize seaports in southern Đại Việt, Suryavarman turned to invade Champa in 1145 and sacked Vijaya, ending the reign of Jaya Indravarman III and destroying the temples at Mỹ Sơn. In 1147 when a Panduranga prince named Sivänandana was enthroned as Jaya Harivarman I of Champa, Suryavarman sent an army consisting of Khmers and defected Chams under the command of the senäpati (military commander) Sankara to attack Harivarman, but was defeated in the battle of Räjapura in 1148. Another stronger Khmer army also suffered the same wretchedness fate at the battles of Virapura (present-day Nha Trang) and Caklyaṅ. Michael Vickery (2011) conjectures that both Räjapura, Virapura, and Caklyaṅ's modern-day precise locations are unknown, but proposes that those medieval locations should be somewhere between Qui Nhon and Phan Rang.
 Unable to overwhelm the Cham, Suryavarman appointed Prince Harideva, a Cham royalty of Cambodian background, as the puppet king of Champa in Vijaya. In 1149, Harivarman marched his army northward to Vijaya, besieging the city, vanquishing Harideva's army at the battle of Mahisa, then executed Harideva along with all of his Cambodian–Cham officials and military, therefore ended Suryavarman's occupation of northern Champa. Harivarman then reunited the kingdom. A royal pretender, Vamsaraja, attacked Harivarman with highland troops but was defeated and escaped to Đại Việt. Later Vamsaraja was crushed by Harivarman and slain during the Battle of Mỹ Sơn in 1150.
 After securing peace with Đại Việt in 1170, Cham forces under Jaya Indravarman IV invaded the Khmer Empire over land with inconclusive results. That year, a Chinese official from Hainan had witnessed elephant duel battles between Cham and Khmer armies, henceforth convincing the Cham king to offer war horse purchases from China, but the offer was rejected by the Song court multiple times. In 1177, however, his troops launched a surprise attack against the Khmer capital of Yasodharapura from warships ploted up the Mekong River to the great lake Tonlé Sap and killed the Khmer king Tribhuvanadityavarman. Multiple-bow siege crossbows were introduced to Champa from Song dynasty in 1171, and later were mounted on the backs of Cham and Vietnamese war elephants. They were deployed by the Cham during the siege of Angkor, which was lightly defended by wooden palisades, leading to the Cham occupation of Cambodia for the next four years. 
 The Khmer empire was in the verge of collapse. Jayavarman VII from the north coalesced an army to battle the invaders. He had campaigned against the Chams in his youth, in the 1140s, and participated in a campaign in Cham capital Vijaya. His army won a series of unprecedented victories over the Cham, and by 1181 after winning a decisive naval battle, Jayavarman had rescued the empire and expelled the Cham.
 In 1190, the Khmer king Jayavarman VII appointed a Cham prince named Vidyanandana, who had defected to Jayavarman in 1182 and had been educated at Angkor, to lead the Khmer army. Vidyanandana defeated the Chams, and proceeded to occupy Vijaya and captured Jaya Indravarman IV, whom he sent back to Angkor as a prisoner. Adopting the title of Shri Suryavarmadeva (or Suryavarman), Vidyanandana made himself king of Panduranga, which became a Khmer vassal. He made Prince In, a brother-in-law of Jayavarman VII, "King Suryajayavarmadeva in the Nagara of Vijaya" (or Suryajayavarman). In 1191, a revolt at Vijaya drove Suryajayavarman back to Cambodia and enthroned Jaya Indravarman V (Jaya Indravarman oṅ Vatuv). Vidyanandana, assisted by Jayavarman VII, retook Vijaya, killing both Jaya Indravarman IV and Jaya Indravarman V, then "reigned without opposition over the Kingdom of Champa," declaring his independence from the Khmer Empire. Jayavarman VII responded by launching several invasions of Champa in 1192, 1195, 1198–1199, 1201-1203. The Khmer later also had double bow crossbows mounted on elephants, which Michel Jacq Hergoualc’h suggest were elements of Cham mercenaries in Jayavarman VII's army. 
 Khmer armies under Jayavarman VII continued campaigning against Champa until the Chams were finally defeated in 1203. A Cham renegade-Prince ong Dhanapatigräma, overthrew and expelled his ruling nephew Vidyanandana/Suryavarman to Dai Viet, completing the Khmer conquest of Champa. From 1203 to 1220, Champa as a Khmer province was ruled by a puppet government led by either ong Dhanapatigräma and then prince Angsaräja, son of Harivarman I, who would later become Jaya Paramesvaravarman II. In 1207, Angsaräja accompanied a Khmer army with Burmese and Siamese mercenacy contingents to battle against the Yvan (Dai Viet) army. Following the dwindling Khmer military presence and voluntary Khmer evacuation of Champa in 1220, Angsaräja took over the reins of government peacefully, proclaiming himself Jaya Paramesvaravarman II, and restored Champa's independence.