[5] The group rose to prominence in 2023 in resisting the Burmese junta in the wake of the 2021 Myanmar coup d'état.

The three armed groups were silent about the coup initially but released a statement reaffirming the alliance's existence in March 2021.

The tensions hit a boiling point following an attack by Arakan Rohingya Salvation Army (ARSA) militants against a Burmese police outpost.

[8] The Ta'ang National Liberation Army predominantly conducted localized operations against the Tatmadaw in northern Shan State prior to the 2021 coup.

[12] This offensive halted in early September 2019, with the alliance releasing a statement that peace talks were held with the Burmese government in Kengtung.

[20] However, AA spokesman Khine Tha Khahe deplored the actions of the Tatmadaw against protesters, calling them "very cruel and unacceptable.

"[21] The TNLA and MNDAA also did not register any clashes with the Tatmadaw immediately following the coup – junta forces instead pulled troops from northern Shan state to southeastern Myanmar to quell insurgents, allowing both groups (especially the TNLA) to exercise de facto control over northern Shan.

The MNDAA and TNLA instead used their respite to train troops and covertly aid local PDF groups in Mandalay.

[28][29] In late 2021, clashes broke out in Kokang after the MNDAA attacked the village of Ei Nie in northern Shan state.

[32] The raid marked the first major attack by the Tatmadaw on a member of the 3BA since the coup, effectively securing de facto MNDAA control over Namphan.

[25] The secretary of the TNLA, Tar Bone Kyaw, stated that the raid cemented the 3BA's position on the junta as hostile.

[9] The TNLA did not conduct any major attacks against the junta forces, but did launch small raids to show power.

[1][35] The operation was in response to a failed junta offensive towards the KIA-controlled town of Laiza in Kachin state, which fizzled out in early October.

[1] In Operation 1027, the Three Brotherhood Alliance captured the city of Chinshwehaw and destroyed dozens of junta bases in the mountains of northern Shan.