On 26 July 2021, the border dispute between Assam and Mizoram took a violent turn when Assam and Mizoram police forces exchanged fire, killing five Assam cops and injuring 60 people from Assam. The firing took place near Lailapur, a town in Cachar district bordering Mizoram. The situation in Lailapur had been tense since October 2020 when a violent clash broke out between people from both the states. A day before the firing incident, eight (unoccupied) farm huts of Mizo farmers were allegedly torched by unidentified people in Vairengte, a border village in Mizoram. In addition, several incidents of encroachment, eviction drives and ransacking of huts along the border have been reported.

According to media reports, what triggered the firing was an alleged attempt by about 200 Assam Police personnel led by senior officials to shut down a duty post near the Vairengte autorickshaw stand bordering Assam. Both the states have presented a different account of the exact trigger of the incident. While Mizoram officials allege that the Assam Police forcibly overran security posts, damaged vehicles and initiated the aggression that prompted the Mizoram police to retaliate, Assam officials insist that the police had gone over to investigate the extent of encroachment and found that Mizoram had disturbed the status quo by squatting in areas about one to three kilometres from the interstate border. Mizoram, in turn, has alleged that Assam has pushed its people, including ‘illegal Bangladeshis’, 10-12 kilometres inside Mizoram’s territory.

Both the states have been making disputed territorial claims since 1972 when Mizoram was separated from Assam as a Union Territory. Mizoram later attained statehood in 1987. At the root of the border disagreement lie two colonial-era notifications. Mizoram considers real the boundary mentioned in the Bengal Eastern Frontier Regulation Act, 1873, which delineated the border between Lushai Hills (present-day Mizoram) and the plains of Cachar district in Assam. In contrast, Assam recognises the 1933 gazetted demarcation as the actual boundary. 

Following the violence on 26 July, the two chief ministers started playing blame game on Twitter, holding the police and civilians (reportedly carrying sticks and rods) of the other state responsible for the incident. Mizoram filed FIRs against Assam Chief Minister Himanta Biswa Sarma and 200 Assam Police officials in connection with the incident. The Assam government, too, filed FIRs against the deputy commissioner of Kolasib and two other officials. Some local organisations reportedly blocked the National Highway 306 in Assam, cutting essential supplies to Mizoram.

Worried by the growing hostility between the two states, the North East Students’ Organisation, comprising major student unions of the northeastern states, released a statement saying that the incident ought to be seen not as an ‘ethnic clash’ but as a ‘border dispute’ resulting from the failure of the state governments to find a permanent solution. 

With the intervention of the Union Home Ministry, fresh negotiations to de-escalate matters between the two states began, with the two chief ministers and Union Home Minister Amit Shah discussing the situation. Following the discussion, both the chief ministers directed their respective state authorities to drop all FIR charges against the accused officials of the other state.

However, on 17 August 17, 2021, tension escalated again along the Assam-Mizoram border after the Assam Police allegedly fired on three Mizo residents. One of them was reportedly injured.
 
In a bid to find a concrete solution to the border disputes in the Northeast, the Union government has decided to demarcate borders of the northeastern states with the help of satellite imaging, the responsibility for which has been given to the North Eastern Space Application Centre dedicated to supporting developmental process in the region using advanced space technology. 

In February 2024, Mizoram and Assam agreed to intensify joint efforts to resolve their long-standing interstate border dispute. Assam Chief Minister Himanta Biswa Sarma invited his Mizoram counterpart Lalduhoma to Guwahati on 9 February 2024 to discuss the matter. Both leaders committed to maintaining peace along the border amid negotiations.

The last round of border talks took place in November 2022. A new round is scheduled on 9 August 2024, in Aizawl. Mizoram Home Minister K Sapdanga will lead his state's delegation, while Assam's Border Protection and Development Minister Atul Bora will head the Assam team.

Sapdanga said that there have been no violations of the status quo since the violent clash in July 2021. However, on 1 August 2024, he accused Assam of constructing a new road in the disputed area, despite clearing other border roads affected by landslides. The Mizo National Front (MNF) and the Mizo Zirlai Pawl students' body have also raised concerns about Assam's road construction activities. Mizoram plans to submit a memorandum to Assam during the upcoming talks.

On 23 August 2023, Mizoram's then Home Minister Lalchamliana said his government has submitted its claim regarding the state boundary, including a list of villages, to Assam in February last year.

Following the formation of the new ZPM government in December 2023, Chief Minister Lalduhoma established a Boundary Committee shortly after assuming office. Headed by Home Minister Sapdanga, the committee was tasked with addressing the long-standing boundary disputes between Assam and Mizoram.

Constituted on 3 January 2024, through a formal notification, the committee comprised the Minister for Environment, Forests, and Climate Change; the state Home Department Commissioner; the Chief Minister's advisor; the Chief Secretary; and the state DGP. To ensure broad representation, the committee also included one member from each of the state's recognised political parties: the BJP, Congress, MNF, ZPM, and AAP.