Battle of Dezful The Battle of Dezful ( also known as Operation Nasr ) , fought in early January 1981 , was a major battle of the Iran - Iraq War . It was the biggest tank battle of the Iran - Iraq War . Three Iranian armored regiment s advanced towards Iraqi forces who had invaded Iranian territory between the towns of Ahvaz and Susangerd . The Iraqi forces were alerted to this movement and feigned a withdrawal . The Iraqis formed three armored brigades into a three - sided box ambush . The Iranians blundered into the ambush and the two tank forces battled for four days in a sea of mud . The Iranians withdrew , leaving many tanks stuck in the mud , or , because of logistical misplanning , out of fuel and ammunition . The condition of the terrain prevented a clean break from the battle and did not allow the Iraqi forces to pursue what was left of the Iranians en force . Prelude . On September 22 , 1980 , Iraqi military forces under the command of Saddam Hussein invaded Iran . Iran , which had been weakened drastically by revolution , offered little resistance . However , their air force ( itself weakened by sanctions and purges ) manage to hit numerous Iraqi military vehicles and military and industrial targets , damaging the Iraqi military and economy . Iraq ' s invasion slowed drastically , and they became bogged down fighting Iranian paramilitary forces in urban actions such as the First Battle of Khorramshahr . By November , the Iraqi invasion force had ground to a halt , and Iran ' s air force had largely defeated their Iraqi counterparts . Iraq ' s navy also suffered destruction . Nevertheless , Iran lacked the strength to drive the Iraqis out immediately . Being under American sanctions , the Iranians could not get spare parts for much military equipment and had to use it sparingly . While Iranian paramiliataries and irregulars had stopped the Iraqi drive , it took over three months for Iran to deploy its military to the region . After the Islamic Revolution in 1979 , the shah era regular army ( including the air force ) had suffered due to purges and lack of supplies and spare part s from their US suppliers , and was no longer the 5th most powerful army in the world . Meanwhile , a new force , the Islamic Revolutionary Guard Corps ( Sepah - e - Pasdaran ) gained prominence . Meanwhile , the conflict between the Pasdaran and the Army took on a new phase after the war began in 1980 . A power struggle began within the new government in Tehran between President Abdulhassan Banisadr and the opposition Islamic Republic Party ( IRP ) , led by Prime Minister Mohammad - Ali Rajai . Banisadr began to support the regular army , while IRP supported the Pasdaran . This severely impeded military operations , and caused a complete lack of coordination . As a result , Iran was virtually unable to launch any major offensives ( other than the air offensive ) . Both armies conducted their operations separately and in a thoroughly uncoordinated fashion , while the Pasdaran carried out much of the combat and getting much recognition . It also led to an erosion of Banisadr ' s revolutionary credentials , as he was increasingly identified as defending and being part of a perceived secular , shah - era entity . Planning . With declining support , President Banisadr convinced Supreme Leader Ayatollah Khomeini in Tehran ( who had the final say in all state matters ) to allow him to take personal command of the regular army . After Banisadr took personal command and arrived at the front , he began planning a major offensive against the Iraqis , codenamed " " Operation Nasr " " ( Victory ) . The attack was to be carried out entirely by the regular army , and if successful would boost Banisadr ' s standing in the still chaotic Iranian political landscape , in addition to trumping the Pasdaran and their supporters . The operation was planned to an armored offensive in Khuzestan province ( the main province that Iraq attacked ) . It was designed to relieve the city of Abadan , which was under what would be a nearly year long siege . It would be preceded by diversionary attacks at Qasr - e - Shirin and Mehran in central Iran . The main attack would be carried out by three armored brigades of the 16th " Qazvin " armored division and the 55th paratrooper brigade of the regular army . The armored thrust would cross the Karkheh River drive from the northeast part of the province past the cities of Susangerd and Ahvaz , down the west bank of the Karun River . At the same time , forces inside Abadan would break out of their positions , and link up with the armored column arriving from the north . The plan depended on total surprise being achieved . Iran ' s armored forces assembled for the attack were larger than their opponents ( consisting of an armored brigade ) , and on paper the plan appeared to be practicable . Despite his title as president , Banisadr was not a military leader . While the flaws of this plan were not apparent to him , they would create serious problems during his campaign . First , Iran ' s army ( having suffered disastrously during the revolution from purges and sanctions ) was simply unable to carry out proper combined arms operations . Many senior generals from the shah ' s era had been lost to purges , and the remaining ones were not as well trained , and / or all too happy to embark on an operation to restore their credibility to the eyes of the regime . Iran ' s armored forces were not skilled in carrying out armored maneuvers even prior to the revolution , and those problems were amplified after the revolution . To make matters worse , much of the regular army infantry forces had been disbanded after the revolution , and there was little time to recall them . Thus the bulk of the tank ' s infantry support should have been the Pasdaran . But since Banisadr was excluding them from this operation , Iran ' s tanks would have less vital infantry support . Without the Pasdaran supporting as infantry , the Iranians were to use their 55th paratrooper brigade from the regular army as infantry support . Even worse , the Iranians did not have sufficient helicopters , artillery , and ammunition to support their advance . The Iranians would use 300 tanks ( M - 47 , M - 60 Patton and Chieftain ) , but didn ' t have the 3 : 1 superiority necessary to guarantee a breakthrough ( and possibly lacked even a 2 : 1 superiority ) . Iran also lacked proper reconnaissance . While Banisadr had tried to alleviate some of the problems , and somewhat restored the Iranian army ' s command structure , it was simply not ready to carry out a major offensive . To make matters worse , the attack had been planned for an unsuitable location . The area around Susangerd was marshy terrain and prone to seasonal flooding , in many ways unsuitable for proper armored maneuver . The Iranians would have to attack slowly in a straight column on surface roads , with the infantry support at the tail end of the column . That meant the tanks would be moving forward unprotected , and with their flanks exposed . Worse , this movement would be easily detected by Iraqi helicopters . The distance the Iranian forces had to penetrate was also exteremely lengthy , and it was easy for the Iraqis to counterattack and reinforce their troops , running counter to Iran ' s plan of achieving surprise . Thus , the stage was set for Operation Nasr . Diversionary Attacks . Iran launched three diversionary attacks prior to Operation Nasr . The first one began on January 4 – 6 , near Qasr - e - Shirin in central Iran . A brigade of regular Iranian mountain troops attacked Iraqi forces that were in a defensive position , blocking the main highway between Tehran and Baghdad . In a pattern which would become all too familiar later during the war , the Iranians infiltrated through the Iraqi positions , and even captured some enemy units . But the battle broke down into a fight for each hill and mountain peak , and the Iraqis rushed reinforcements . While Iran gained 8 kilometers , they did not achieve any significant tactical advantage . The second attack involved other Iranian mountain troops infiltrated and attempted to liberate Mehran . The end result was similar to the previous battle . The third attack was more serious . It involved an Iranian mechanized division attacking Iraqi forces west of the Karun River in the vicinity of Ahvaz . The goal of the battle was to drive the Iraqis out of artillery range of the city . The terrain was more suitable for vehicles ( although it did not favor Iran ) , and the road network was good . They achieved surprise , and drove the Iraqis back several miles , however Iraq remained within artillery range of the city and the Iranians took moderate to heavy losses . Operation Nasr . The main attack began on 5 January . The attack began with a short artillery bombardment . The Iranian forces , using pontoon bridges , crossed the Karkheh River . The Iranians used 300 tanks . Due to the marshy terrain , they were confined to the paved surface highway . Because of that , the Iranians assembled their forces in a long row of columns . The first three columns consisted of armored brigades , and the final column was the infantry support . The infantry was thus behind the tanks , and Iran ' s flanks were completely exposed . The Iranian forces began to move down the paved road around Susangerd and Dezful . They moved very slowly , and each column moved separately . Unknown to the Iranians , their plans had already begun to go awry when Iraqi observation aircraft spotted the column moving south towards Abadan . Thus their plans for surprise had been foiled . The Iraqis immediately began planning their action . Iraq moved their 10th Armored Brigade , and positioned them on the Iranian line of advance on the road . The Iraqis dug their tanks into a hull - down position , meaning they were dug into the mud of the marshes and used as static pieces . While the Iraqis often lacked the skill to maneuver , and regularly dug their tanks in , in this instance it would prove to be successful , because the mud of the marshes would hamper armored maneuver . The Iraqi tanks ( Soviet T - 62 and T - 55 ) were dug into positions both in front of and on the side of the Iranian line of advance . The Iraqis were also supported by Mi - 8 helicopters . Thus the Iraqi trap was set . On 6 January , the next day , Iranian forces came into contact with the Iraqi armor . Iran ' s shortage of recoinassance proved to be disastrous as they failed to see the approaching trap . The Iraqis began firing at the Iranian tanks from the front and both sides . The Iranians tried to drive through the Iraqi forces in an armored spearhead , but took heavy losses . They then tried to maneuver . But that involved driving their tanks off the paved road , and into the mud . Iranian tanks then got stuck in the mud . The first Iranian brigade was decimated , and many tanks were destroyed or abandoned in the mud . Nevetheless , the Iranians refused to abort the attack , and their next brigade moved into action . The second Iranian brigade advanced , and the results were similar . Iranian helicopters ( AH - 1 Cobra s ) also joined the battle , destroyed several dug - in Iraqi tanks , but they were outnumbered by Iraqi helicopters which inflicted heavy losses on the Iranian tanks . The Iraqis also had anti - aircraft weapons as well , and several Iranian helicopters were shot down . To make matters worse , Iraqi mechanized infantry with anti - tank weapons joined in , turning the battle into a slaughter for the Iranians . Fighting took place at close range and was brutal . Nevertheless , the Iraqis also took many losses , because their tanks were dug in and because of the superior pre - revolutionary Iranian training . Just when things were going badly , Iraqi aircraft also bombed the pontoon bridge across the Kharkeh River , trapping the Iranian tanks and preventing their retreat . Iran ' s infantry was also stuck on the opposite bank ( they hadn ' t moved into action yet ) and separated from joining the battle . Iranian helicopters attempted to fight back , but they were attacked by Iraqi fighter jets , which destroyed or damaged several helicopters . By 8 January , the entire Iranian attack was in chaos . Many tanks from the first two brigades had been lost , either destroyed , or stuck in the mud and abandoned . The third Iranian brigade attempted to continue the attack , but could make little headway . Instead , Operation Nasr was aborted , and the Iranians moved to retreat . The infantry force ( which never had a chance to join the battle ) instead moved into a defensive position to prevent an Iraqi counterattack . Iranian engineers at the last second managed to rebuild the pontoon bridges over the Kharkeh river , and the third Iranian tank brigade managed to break away from the combat and retreat from the Iraqi forces and move back across the Kharkeh River . Meanwhile , during the debacle at Dezful , Iranian infantry forces at besieged Abadan attempted their breakout , in order to link up with the armored column . Even if they 16th armored division had not been defeated in battle , it was unlikely that they would have been able to reach them . The Iranian infantry took heavy losses and were forced to retreat back to Abadan . Aftermath . The Iraqis had heavily defeated the Iranians . While the Iranians had been a powerful force prior to the revolution , the damage inflicte by the revolution had made it possible for the Iraqis to gain a victory like this . Nevertheless , poor Iraqi training saved the Iranians from a total rout . The Iraqis primarily dug in their tanks into the ground to act as static artillery , and while that worked at the fighting around Dezful and Susangerd , it meant that they were unable to follow up their victory and destroy the Iranians . Instead , they remained dug in as the Iranians withdrew . A minor Iraqi counterattack with helicopters and some armor was beaten back by Iranian forces . For the Iranian military , this major defeat had serious implications . Iran had lost between 88 and 214 tanks ( depending upon the source ) , at least 100 other armored vehicles , some heavy artillery and a large portion of the 16th armored division . Many armored vehicles had been captured intact as they had been abandoned or stuck in the mud , and were put on display in Iraq ( some were later even sold to Jordan , while others remained in storage until the 2003 US invasion ) . The losses would have been much worse had not the Iranians managed to reassemble their pontoon bridge . Prior to the revolution , Iran had had 1 , 700 tanks ( which dwindled to 1 , 000 usable ones after the revolution ) . With their defeat at Dezful , at least 10 - 20 % of that entire force was destroyed , a major weakening of Iranian military power . To make matters worse , with US - led sanctions on Iran , those tanks could not be replaced while the Iraqi ones could easily be ( since they weren ' t under an embargo and had the support of the west ) . Despite their decisive victory , 50 - 100 Iraqi tanks and other armored vehicles were destroyed . Since they fought from static positions , they were easier targets . Nevertheless , their losses could be replaced , while the Iranians ' could not . The defeat at Dezful had major political implications in Iran . President Banisadr had been expecting that a major victory would help increase his political standing and help silence his ever - critical opponents . Instead , exactly the opposite happened . His approval rating dropped drastically , and his opponents attacked him even more fiercely . Worse , the army , which he supported , was now discredited even further . By June 1981 , things had gotten so bad for Banisadr that Iran ' s Parliament led by the IRP and Prime Minister Rajai impeached him . The Ayatollah Khomeini , which had played the role of a " neutral arbiter " and had through the past year had sought to settle the differences between Banisadr and his opponents , finally gave up on him , and approved his impeachment . Banisadr fled the country in disguise with a defecting air force pilot to avoid arrest . Banisadr was replaced by an unofficial junta , led by the now President Rajaii , the new Prime Minister Javad Bahonar , and the Speaker of Parliament Ali Akbar Hashemi Rafsanjani . Iran became a virtual one - party state led by the IRP for the duration of the war . The impeachment of Banisadr began a several month period of near civil war and terror in Iran . At least several hundred government officials were killed in assassinations and bombings ( which killed Rajai and Bahonar , and nearly Rafsanjani ) . The Iranian regime unleashed their own wave of terror , torturing and executing over 3 , 000 members of the opposition , and purging the regular army once again . They eventually suppressed most of their opponents ( including dissident clerics ) . By September , the political situation was improving and with the government under the control of the hard - liners of the IRP , Iran ' s military effectiveness drastically improved . The hardliners were willing to benefit from the army , and with no power struggle , Iran was able to fight effectively again . Both as a result of heavy equipment losses , and a decline in confidence , the Iranian army with their regular tactics were not seen as important . Instead , the Pasdaran infantry with their unconventional tactics became even more prominent . Nevertheless , the army and Pasdaran would be able to display a unity that would help them drive the Iraqis out of Iran , with the Pasdaran launching human wave attacks , and the regular army using their tanks and artillery to support them .