The November 13, 2021 ambush near Sialsih in Manipur’s Churachandpur district was claimed by the PLA and MNPF. The attack killed Colonel Tripathi, his wife Anuja, their son Abir and four Assam Rifles personnel, with several others injured.
BY Navin Upadhyay
August 24, 2026: The arrest of self-styled People’s Liberation Army (PLA) captain Thiyam Boycha Singh alias Balin over the weekend has revived scrutiny of one of the deadliest militant attacks on security forces in Manipur in recent years. Balin, who carried a ₹4 lakh reward announced by the National Investigation Agency (NIA), is among the cadres accused of participating in the November 2021 ambush that killed Assam Rifles Colonel Viplav Tripathi, his wife, their young son and four other personnel.
His arrest, however, has done little to alter the larger picture. Nearly five years after the attack, most of the militants named by the NIA remain absconding, including two accused for whom the agency announced the highest reward of ₹8 lakh each.
Balin was arrested in an intelligence-led joint operation by Assam Rifles and Manipur Police in Thoubal district. He was among the ten cadres of the PLA and Manipur Naga People’s Front (MNPF) named by the NIA in connection with the ambush. Investigators had accused the group of planning and executing the attack on the convoy of Colonel Tripathi, then Commanding Officer of 46 Assam Rifles.
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The November 2021 ambush
The attack took place on the morning of November 13, 2021, near Sialsih village, also referred to as Sehken, along the Indo-Myanmar road in Churachandpur district.
Colonel Tripathi was returning to the 46 Assam Rifles battalion headquarters at Khuga after visiting a forward company post at Behiang, close to the Myanmar border. His wife Anuja and their young son Abir were travelling with him, along with members of a Quick Reaction Team.
The convoy, comprising four vehicles, was moving through a narrow stretch of road surrounded by dense vegetation when militants launched the attack. Investigators said an improvised explosive device was detonated before the attackers opened fire with automatic weapons from multiple directions.
Colonel Tripathi, his wife and their son were killed along with four Assam Rifles personnel — Riflemen Suman Swargiary, Khatnei Konyak, R.P. Meena and Shyamal Das. Several other personnel were injured.
The PLA and MNPF subsequently claimed responsibility for the attack. In their statement, the militant groups said they had not known that Colonel Tripathi’s family was travelling in the convoy.
The killing of the officer and his family sent shockwaves across the country and prompted a major investigation into the planning, logistics and execution of the ambush.
Colonel Tripathi’s bullet-riddled vehicle, carrying his wife & six year old son abhir, bore the horrific scars of the cowardly ambush. pic.twitter.com/XV8kviXK4Y
— J Shakur (@JShakurB) August 23, 2026
NIA names 10 accused
The NIA took over the investigation and re-registered the case as RC-33/2021/NIA/DLI. In January 2022, the agency publicly named ten cadres belonging to the PLA and MNPF and announced cash rewards for information leading to their arrest.
The two most wanted accused were self-styled lieutenant colonels Chaoyai alias Pukhrambam Mani Meetei and Sagolsem Inaocha alias Ranjit Naorem. The NIA announced a reward of ₹8 lakh each for their arrest.
A ₹6 lakh reward was announced for Sanatomba, while ₹4 lakh rewards were announced for Khaba, Khwairakpa, Nongyai, Joseph, Rocky, Balin and Kanta.
The reward structure reflected the importance investigators attached to the accused and their alleged roles in the attack. Additional names connected with the case have also appeared on agency absconder lists over the years.
Few arrests in nearly five years
Despite the passage of almost five years, the investigation has resulted in relatively few arrests among those publicly named by the NIA.
An MNPF cadre was detained in 2022. Sanatomba was arrested in 2025. Balin is the latest major accused to be taken into custody.
Several others named in the case remain at large, including the two accused carrying the highest ₹8 lakh rewards.
The limited number of arrests has kept the 2021 ambush an unresolved security concern for investigators. Security agencies have suspected that some of the absconding cadres could still be operating from concealed bases in Manipur or from locations across the porous India-Myanmar border.
The terrain and the movement of insurgent cadres across the border have historically complicated efforts to track down wanted militants. Investigators have also had to contend with shifting militant networks and the continuing security challenges in Manipur.
Balin’s arrest brings case back into focus
Balin’s arrest is therefore significant not only because of his alleged role in the 2021 attack but also because it demonstrates that security agencies continue to pursue suspects several years after the ambush.
He had been carrying a ₹4 lakh NIA reward and was among the accused who had remained beyond the reach of investigators despite repeated efforts to locate them.
His interrogation could potentially provide investigators with information about the planning of the attack, the movement of cadres before and after the ambush, the weapons and explosives used, and the whereabouts of other suspects.
For the families of those killed, however, the arrest comes nearly five years after the attack.
Colonel Tripathi, his wife and their young son were travelling together that morning, along with the Assam Rifles personnel assigned to protect the convoy. Their deaths transformed what was already a serious militant attack into a particularly tragic episode, as an officer’s family was caught in an ambush intended for a security convoy.
With Balin now in custody, attention is likely to turn once again to the remaining accused — particularly the two senior cadres carrying ₹8 lakh rewards — and whether the agencies can bring the principal absconders before the law.
The rewards announced by the NIA in 2022 are understood to remain in force, keeping the case active even as the fifth anniversary of the ambush approaches.
