1947–1959 The KNU was founded in 1947. Following Myanmar's independence in January 1948, KNU leaders instructed local organisers to establish local defence militias, collectively grouped under the
Karen National Defence Organisation in their districts. The KNU launched its armed campaign against the Myanma government in early 1949. By the early 1950s, factions within Karen politics were influencing the strategic posture of the KNU. In 1953,
Mahn Ba Zan and other KNU leaders established the
Karen National Unity Party (KNUP), a communist-influenced group that supported a shift leftward in KNU politics.
1960–1969 By 1960, KNUP members had become the dominant figures within KNU structures, despite the KNUP being a "minority" tendency within Karen politics, as described by
Paul D. Kenny. The KNUP was strongest in the
Irrawaddy Delta. Under KNUP influence, the KNU was centralised, the KNLA was reorganised along Maoist lines, and agricultural cooperatives were created in some KNU-controlled villages. By 1963, the KNU numbered approximately 10,000. and the 11th KNU congress was held in 1995. Bo Mya dominated the KNU leadership for three decades from 1976 to 2000. For many years, the KNU was able to fund its activities by controlling black market trade across the border with
Thailand, and through local taxation. After the failed
8888 Uprising of the Myanmar people in 1988, the
Myanmar military government turned to China for help in consolidating its power. Various economic concessions were offered to China in exchange for weapons. The
Myanmar Army was massively expanded and began to offer deals to groups fighting the government. The groups were offered the choice of cooperating with the military junta or being destroyed. In 1994, a group of
Buddhist soldiers in the KNLA, citing discrimination by the KNU's overwhelmingly Christian leadership against the Buddhist Karen majority, broke away and established the
Democratic Karen Buddhist Army (DKBA). They were led by
U Thuzana, an influential
Karen monk. The DKBA quickly agreed to a ceasefire with the Myanmar army and was granted business concessions at the expense of the KNU. The KNU and DKBA have since been in regular fighting, with the DKBA actively supported by the Myanmar army. The KNU's effectiveness was severely diminished after its headquarters were captured in the
Fall of Manerplaw, near the Thai border, in 1995.
2000–2009 The 12th KNU congress was held in 2000, and the 14th KNU congress was held from 6 to 20 October 2008. In 2009, the KNU's fighting force was reduced to around 3000 to 5000 soldiers, and on 25 June 2009 the KNLA's Brigade 7 headquarters was overrun.
2010–present On 2 November 2010, the Karen National Union became a member of an alliance which included the
Karenni National Progressive Party (KNPP), the
Chin National Front (CNF), the
Kachin Independence Organisation (KIO), the
New Mon State Party (NMSP) and the
Shan State Army North (SSA-N). In January 2012, Myanmar's military-backed civilian government signed a ceasefire deal with the KNU in
Hpa-an, the capital of eastern
Kayin State.
Aung Min, the Railway Minister, and General Mutu Sae Poe of the KNU led the peace talks. In March 2012, a senior political leader of KNU, P'doh
Mahn Nyein Maung, was found guilty of
high treason under the Illegal Association Act, for his involvement with the Karen rebellion and sentenced to 20 years. He was freed soon afterward and sent back to Thailand. The Karen National Union held its 15th congress at Lay Wah on 26 November 2012. This meeting was held at a pivotal moment in the KNU's history, as it occurred at a time of political in-fighting in regards to how the KNU should negotiate a ceasefire agreement with the Myanmar government. From 30 October to 2 November 2013, an unprecedented meeting took place at the
Kachin Independence Organisation headquarters in
Laiza. For the first time, representatives of 17 armed ethnic opposition groups were able to meet in Myanmar with the consent of the government. The conference resulted in the formation of a 13-member Nationwide Ceasefire Coordinating Team (NCCT) and the signing of an "11-Point Common Position of Ethnic Resistance Organisations on Nationwide Ceasefire" or the Laiza Agreement. The NCCT's current mandate was to take responsibility on writing the
Nationwide Ceasefire Agreement based on mutual understanding between the different armed groups in the NCCT. At the Law Khee Lah Conference, it was agreed that the NCCT had the mandate to discuss and change the document technically, except at the policy level. When the final document was ready, the respective ethnic organisation leaders decided and discussed with the Union Peacemaking Working Committee (UPWC) on the nationwide ceasefire. On 15 October 2015, the KNU signed the
Nationwide Ceasefire Agreement (NCA) with the government of Myanmar, along with several other insurgent groups. In September 2016, KNLA fighters began clashing with members of the
Mon National Liberation Army (MNLA), the armed wing of the
New Mon State Party (NMSP), in the
Tanintharyi Region. Both the KNU and NMSP were signatories of the
Nationwide Ceasefire Agreement (NCA) at the time of the fighting. A temporary bilateral truce was reached between the two groups on 14 March 2018. Tensions between the KNU and the Tatmadaw increased as unrest swept the country following the
2021 Myanmar coup d'état. On 27 March 2021, KNU Brigade 5 overran a Myanmar Army base near the Thai border, killing ten soldiers including a deputy battalion commander. The Myanmar army launched multiple airstrikes on Karen villages in retaliation. In 2021, KNU became a member of the
National Unity Consultative Council. Following the coup, the KNU launched an investigation on Nerdah Bo Mya, a commander of the Karen National Defence Organisation (KNDO), the KNU's other main armed wing, for his role in the extrajudicial execution of 25 men. He refused to cooperate with the investigation and instead formed a splinter group, the Kawthoolei Army. The KNU disputes this claim by asserting that they control 90% of the border area. On 28 August 2025, the
State Security and Peace Commission Ministry of Home Affairs declared the KNU as an unlawful association and its Counter-Terrorism Central Committee designated the KNU as terrorist group. On 14 November 2025, the KNU and its allied forces recaptured the
Myanmar–Thai border town of Mawdaung at the
Singkhon Pass, reclaiming the area for the first time since its seizure by the junta in 1990. On 30 March 2026, the KNU joined the newly-formed
Steering Council for the Emergence of a Federal Democratic Union (SCEF) with the
Kachin Independence Organisation,
Chin National Front,
Karenni State Interim Executive Council,
National Unity Government, and the
Committee Representing Pyidaungsu Hluttaw. ==Conditions of ceasefire==