Direct proof of use
Open-source documentation for the BTR-40M in the 2014 Yemen Civil War is narrow. Oryx listed BTR-40M under armored personnel carriers in service with the Yemeni Army before the Houthi takeover of Yemen in 2014 and 2015, and described the list as equipment available to Yemeni parties on the battlefield.
A Thai National Intelligence Agency country profile later described Houthi forces as acquiring weapons and equipment from captured Yemeni government bases between September 2014 and February 2015, including BTR-40-family armored vehicles. The profile names BTR-40 rather than the BTR-40M designation, so the strongest claim is that BTR-40M was documented in the pre-war Yemeni Army inventory and that BTR-40-family vehicles entered Houthi-aligned captured-equipment holdings during the same takeover period.
Sources: Handbook Of Pre-War Yemeni Fighting Vehicles, Republic of Yemen Country Profile 2022
Timeline
In September 2014, Houthi forces allied with forces loyal to former president Ali Abdullah Saleh seized Sanaa, beginning the conflict phase represented here. The Associated Press later summarized the March 2015 Saudi-led intervention as backing Yemen's internationally recognized government against the Houthis.
For the BTR-40M record, the relevant equipment window is the 2014-2015 takeover period. Oryx's September 2015 inventory placed BTR-40M in the pre-takeover Yemeni Army armored-personnel-carrier inventory, while the Thai NIA profile described Houthi acquisition of BTR-40-family vehicles from captured government bases during September 2014-February 2015.
Sources: AP Yemen War Timeline, Handbook Of Pre-War Yemeni Fighting Vehicles, Republic of Yemen Country Profile 2022
Narrative
The BTR-40M entry is best treated as legacy armored mobility rather than a separately documented combat system. The Oryx inventory separates BTR-40M from BTR-40 in Yemen's pre-war armored personnel carriers, but it does not define the modification standard, identify a unit, or describe a specific battle use.
The later Houthi equipment context is family-level. The Thai NIA profile says Houthi forces obtained BTR-40 and BTR-60 armored vehicles from captured Yemeni bases, and Defense Express separately reported that Houthis claimed BTR-40s among their armored holdings. Those sources support captured-equipment and possession context for BTR-40-family vehicles, but they do not establish a distinct BTR-40M engagement, armament fit, or confirmed battlefield incident.
Sources: Handbook Of Pre-War Yemeni Fighting Vehicles, Republic of Yemen Country Profile 2022, Defense Express Yemen Forces Assessment