During the Insular Wars against the Tau, forces of the traitor Major General Bludmey commander of the Interplanetary Revolutionaries, aided by a small xeno detachment, assaulted the planet of Engir defended by 60th, 74th and 109th Lechian Rifles and 68th Lechian Armored regiments of the Lechian Legion. After repealing the invasion, surviving legionnaires have been incorporated into the 109th Lechian Rifles that in turn achieved the status of veteran regiment and has been renamed 109th Lechian Old Guard.
Despite its harsh living conditions, Engir has been an important trade hub since the Dark Age of Technology. To defend the capital city of Engir’enr and its artificial Gravitational Wells against invasion from space, G’urs Att’an [translated as fortifications or castle] had been built on top of the low mountain range between it and the Mugar'ali Steppes, that fell into the Green See hundred kilometers further south. During the opening days of the Insular Wars against the Tau Engir was considered of secondary importance and therefore was seized by the Imperial forces with little opposition. That is why, after suffering losses in the fights on other planets, some Lechian units were sent there in 810M41 to serve as a garrison and to rest.
M’urs Att’an was manned by roughly 15 600 Lechian soldiers from the 74th and 109th Lechian Rifles. The unit was commanded by Colonel Franciszek Młokosiewicz of 109th. Smaller garrisons were placed in the nearby towns of Sa’ijm (6300 legionnaires from 60th Lechian Rifles and 35 tanks from 68th Lechian Armored under Lieutenant Colonel Bronisz) and Al’orim (1200 infantrymen from 60th and 18 tanks from 68th under Captain Eustachy Chełmicki). All of these forces formed part of the Army Corps of Lord General Militant Horace von den Zigzaur, that was the overall commander of Imperial forces in the region.
In the latter half of the 810M41, Major General Bludmey commander of the Interplanetary Revolutionaries, traitors that sided with the Tau, decided to lead an expeditionary force towards Engir and seize it by surprise. The pro-xeno partisans informed him about the weakness of the defenders and lack of reserves. Bludmey gathered a field force of 23 Regiments of the Interplanetary Revolutionaries, another two composed of the deserters from the Imperial Guard, a siege artillery unit and a Tau Fire Warriors Cadre. The initial expedition numbered some 170 000 men and 1500 tau, excluding naval staff and crew. They boarded a small fleet consisting of two Tau frigate-class ships, five ex-Imperial vessels and several dedicated transports.
In the ending days of 810M41, the invasion forces reached the borders of the system and proceeded towards the planet of Engir. After fending off small Imperial fleet hanging in orbit Bludmey ordered his transports into the planet's atmosphere, but below the range of the Imperial surface-to-space guns, meanwhile his own fleet exchanged fire with lance batteries of G’urs Att’an. Lacking manpower Lechians weren't able to stop the transport ships and traitors landed safetly on the coasts of the Mugar'ali Steppes and were joined on the beach by a small number of pro-xeno partisans. Defenders raised the powerful shields over the Engir’enr protecting the city and traitor's fleet had to withdraw not being able to pierce it. After the landing was complete, Bludmey led his Interplanetary Revolutionaries north, three days later they arrived in front of the G’urs Att’an and the traitor general sent an emissary to convince the Lechian commander to surrender the castle. "Come and take it if you dare." Młokosiewicz replied and with the failure of the negotiations Bludmey ordered his siege guns to open fire.
Bludmey attempted a frontal attack on the castle walls. However, because his units were suffering heavy losses and weren't able to breach Imperial defences he was forced to order a retreat. Despite numerical inferiority, the Lechians held out. Sergeant Zakrzewski even managed to destroy one of the siege engines, those that remained withdrew out of the range of Lechian guns. Over the course of next few days traitors were regrouping their forces in preparation to another assault. In the meantime, the Lechian garrisons of Sa’ijm and Al’orim, alarmed by the ongoing battle, forced march making their way towards the G’urs Att’an to try and joined up with the defenders.
On the morning of the Day of Emperor's Ascension artillery bombardment became heavy and the traitor cannons destroyed one of the castle sections. To counter the threat, Colonel Młokosiewicz decided to execute a surprise attack on the enemy artillery positions. Leaving the castle guarded mostly by the wounded, he led the remaining legionnaires in a sally. The besiegers were taken by surprise and, despite huge numerical superiority (approximately 10:1), the Interplanetary Revolutionaries protecting the siege artillery battery redoubt retreated in disorder. The guns were turned away from the castle and the Lechians started shelling the traitor positions. Artillery fire made the regrouping of troops much more difficult for the besiegers.
After about half an hour, Major General Bludmey managed to reorganise his troops and ordered the assault of the artillery emplacement occupied by Imperial forces. This time Tau led the charge and the outnumbered defenders were forced to withdrew towards the castle. However, before the traitor and Tau forces could push any further, they were attacked on their left flank by the Lechian garrisons of of Sa’ijm and Al’orim that had just arrived on the battlefield. 7500 rested and well-equipped legionaries supported by 53 tanks under Lieutenant Colonel Bronisz distracted the besiegers long enough to let the withdrawing Colonel Młokosiewicz regroup his force and strike the right flank of the invaders. This near-simultaneous attack of Lechian units, supported by once more captured siege guns, surprised the enemy forces, which soon began to waver. After Major General Bludmey was killed by the Lechians, the panic spread amongst his troops, they started a chaotic withdrawal but were slaughtered mercilessly by the loyalist. Some remnants of the Tau Cadre were able to reach the landing zone and board the transports, but they were later shot down when trying to get into the outer space.
After repealing the invasion, surviving legionnaires have been incorporated into the 109th Lechian Rifles that in turn has been elevated into the rank of the Old Guard Regiment.
Although the Battle of Engir was a great Imperial victory it did not have any significant influence on the outcome of the war, because shortly after it ended Saint Lorantia the Emperor's Torch declared the crusade in that region and Steel Templars Space Marines answered her call. With the help of Emperor's favourite sons Insular Wars ended with swift Imperial victory.