As the frontline kept approaching Romania, there was an evergreater need of aviation to support the Romanian armies facing the Soviets. In the same time, the American 15th USAF had established bases in southern Italy and from this bases it tried to destroy the Romanian oil industry by repeated massive bombing raids, starting from the 4th of April 1944. To face these dangers, ARR command mobilized virtually everything they had in an all-out attempt to defend the country. The 1st Air Corps, which comprised the best planes and pilots available remained at first on the east front, whilst the 2nd Air Corps, created on the 1st of April 1944, grouped most Romanian-built planes and had the task of defending the country against the American bombers. As we'll see later, they would eventually switch places, as the 15th USAF proved to be a far more powerful opponent than the VVS.

Because the Russians were getting evercloser to the borders of Romania, the ARR gathered every single bit of offensive power it had to stop them. The old IAR-37 reconnaissance planes, PZL P-11f fighters and Nardi FN-305 advanced trainers were equipped with bomb launchers in order to be utilized as light bombers on the east front. It was intended to create one more assault group ( the 11th ), but due to lack of planes only one squadron ( the 38th ) was created. Since by this stage of the war the IAR-80 and IAR-81's were clearly outclassed by most of their opponents, the IAR factory started to manufacture Bf-109G's under license, and it was hoped to equip every fighter group with Romanian built 'Gustavs'.

The prelude of this campaign can be traced back to as far as the 12th of June 1942, when 13 American B-24's ( the very first planes of this type arrived in Europe ) flew an isolated raid over Romania, under the codename "Operation Halpro". The planes took off from the Fayid airfield in Egypt, flew independently towards Romania, where they dropped their bombs ( without doing any serious damage ), and finally landed on airfields in the Middle East. Whether this was a serious attack or just a warning, it remains unclear ( although it's hard to believe the Allies really expected to deliver a serious blow with just 13 bombers ). American losses on this occasion remain a subject for debate : Romanian sources claim that the only fighter scrambled on that day ( an IAR-80A of the 8th Fighter Group ) intercepted and shot down a B-24 'Liberator' near the village of Viziru, whilst American records don't show any loss. Anyway, no more attacks followed until mid 1943, when the infamous "Tidal Wave" operation took place.

For the rest of 1942 and early 1943, Ploiesti remained a target the Allied leaders desperately wanted to hit. To understand why, one must realize that half the high-octane aviation fuel needed by the Luftwaffe for its fighters and bombers came from Ploiesti. It was here that the highest quality 90-octane aviation fuel was produced and there was no other factory or refinery in Europe which could provide the same high-quality commodity. Virtually all the gas who fueled Rommel's panzers in their drive towards Egypt also came from the Romanian refineries. For a long time, British leaders remained convinced the only way to stop the Afrikakorps was to destroy their source of oil. In January 1943, at the Casablanca conference, Churchill managed to persuade Roosevelt to order a massive raid against Ploiesti for that year. The American and British planners considered that by destroying the refineries they could shorten the war by six months. Upon hearing the news, Sir Arthur Tedder, air marshal of the RAF, immediately offered fuel and bombs from its North African deppos for the raid. Colonel Jacob Smart was tasked with planning and organizing the raid. The American air attaché in Cairo, colonel Bonner F. Fellers declared the Ploiesti was " by far the most important objective in Europe", a vital strategic target.

Colonel Smart decided the best solution was a daylight raid executed by the Liberators of the American 8th and 9th Air Forces, starting from airfields in Libya. It would have to be a raid without fighter cover, since no Allied fighters could reach Romania from bases in Africa. Therefore, Smart came up with the idea of attacking at very low altitude in order to achieve surprise and maximum bombing accuracy. The B-24's would arrive over the target area in formations of 8 to 12 planes, dropping their 250 kg and 500 kg delayed action bombes from altitudes varying between 100 and 150 meters. This way, Colonel Smart hoped to avoid enemy fighters and the heavy AA guns. He was so confident in his plan, that he wanted to fly with the first wave but was forbidden at the last moment.

What the Allies didn't know was that they had dangerously underestimated the strength of the defenses. The Romanian 4th AA Artillery Brigade ( made up of the 5th and 7th Regiments ) and the German 5th Flak Division ( made up of the 180th and 202nd Regiments ) were deployed around Ploiesti and ready to meet the attackers. The Romanian brigade had 21 heavy batteries ( 15 of them had German 88 mm Flak guns, 68 guns in total and the rest had Romanian built Vickers/Resita 75 mm guns ) and 6 light batteries ( all equipped with 20 mm guns, 78 of them ). The German 5th Flak had 21 heavy batteries ( they had 88 mm and 105 mm Flak guns, 96 in total ) and 10 light batteries ( 132 pieces altogether ). It's worth mentioning that three of the German heavy batteries were mounted on railway flatcars, which gave them excellent mobility. Between them, the Romanian and German units had 210 light AA guns and over 180 heavy AA guns. As normal, the refineries were protected by fighters as well. The Romanian 6th and 4th Fighter Group were based in the area, as well as the 53rd Fighter Squadron and the 52nd Night Fighter Squadron. Elements of all these units were scrambled against the Americans and enjoyed some success, claiming 10 confirmed B-24's. The only Luftwaffe unit who also intervened that day was the JG4, who sent its Bf-110G's and Bf-109G's against the bombers. A German Freja type radar station ( codenamed Palermo) had long since been installed and proved invaluable during the raid.

Between 12.30 and 14.45PM all American planes arrived over the target area, after some formations were engaged by Romanian and German fighters.A hale of antiaircraft fire greeted the B-24's as they headed towards their target. The 20 mm guns proved very effective against the huge, low-flying bombers, and many planes fell victim to their shells. By 14.45PM it was all over and the Americans were heading home.

Of the ten refineries targeted by the Allies, only 5 were hit but none was completely destroyed or forced to stop production ( just two refineries, namely Columbia and "Creditul Minier" lost 70% and 75% of their capabilities, whilst the other three suffered damage only up to 20-35% of capacity ). The other 5 were completely untouched, and them alone could easily maintain or even increase oil production if necessary. A total of 53 B-24's had been shot down ( 10 by Romanian fighters, 7 by German fighters and the rest by antiaircraft fire ) and 8 more were forced to crash land in Turkey. 23 heavily damaged bombers barely made it to Allied bases in Cyprus, Malta or Sicily. Of the 88 'Liberators' that did return to Benghazi, no more than 33 were considered "ready to fly" the next day. Over 310 American airmen were killed, 140 were captured and 79 more were interned in neutral Turkey. Off those who did made it back to base, over 450 had been wounded in the fierce battle. Romanian losses were just 5 fighters shot down ( the Germans lost 2 more ).

In early 1944, the ARR's 1st Air Corps was still on the east front, trying to stop the Soviet forces. As the frontline advanced westwards, the Corps kept retreating and by the summer of 1944 it was flying from bases inside Romania. By this time, the ARR commanders had gathered together virtually every plane who could still fly and created the 2nd Air Corps on the 1st of April 1944. It was also deployed on the east front, covering the seaside and the Danube Delta.

The table below show the composition of both Air Corps in the summer of 1944 :

By the spring of 1944, the American 15th USAF had been redeployed from its North African bases to airfields in southern Italy, mainly around the major base of Foggia. From here, it was planned to return in force over Romania, particularly over the refineries near Ploiesti. Initially, the 15th USAF was made up of some 16 heavy bomber groups ( equipped with B-17 Flying Fortresses and B-24 Liberators ) and 5 fighter squadrons ( equipped with P-51 Mustangs and P-38 Lightnings ), but later it would receive additional units ( 5 more heavy bomber groups and two more of fighters ). Altogether, the Americans could call upon over 800 bombers and 350 fighters. They enjoyed a numerical superiority of 5:1 on every raid, and the difference would increase as the battle progressed. The British were also present at Foggia, where the British 205th Bomber Wing was based and ready to strike at targets inside Romania. It seemed that the Allies would have no problems with the ARR, at least on paper.

On the 4th of April, the first massive American raid over Romania since 1943 took place. The B-24's of the 47th Wing hit the capital, Bucharest. Their targets were the city's railway station and the marshaling yard. Results were considered not good enough, so the bombers came back 5 more times until the end of April : on the 5th and the 15th they bombed Ploiesti, on the 16th the city of Brasov and the IAR factory, on the 21st it was Bucharest's turn again, on the 24th Ploiesti and Bucharest were attacked simultaneously.

June brought no ease in the American pressure, with strikes targeted primarily against Ploiesti and Bucharest on the 2nd, 6th, 10th, 11th, 23rd, 24th and the 28th of June. By this stage, all of the objectives the 15th USAF aimed to destroy should have been long since bombed to the ground, but somehow, a combination of strong defense and great reconstruction work kept the refineries and other industry working. Therefore the bombers continued to return over the same targets time after time during July, when they came on the 3rd, 4th, 9th, 15th, 22nd, 26th, 27th and 28th. One target in particular ( the "Romanian-American" refinery ) seemed impossible to destroy, as the American bombers hit it more than six times, claiming each time to have destroyed it completely, only to discover that they had to fly "one more" raid. The last battles in which the ARR had to face the 15th USAF came in August. It was in this period that the defenses were beginning to crack under the weight of the American onslaught. After the ARR lost one of its heroes, the 2nd scoring ace captain Serbanescu on the 18th of August, it was ordered that no Romanian fighters should try to engage the Americans. The odds were so heavily against the Romanian pilots that it was clear any more engagements could only result in more losses, losses which the ARR simply could not afford. Fortunately, the raid on the 18th was the last one, because five days later Romania signed a cease-fire agreement with the Allies and quit the Axis.

Initially, the Romanian 1st, 5th and 6th Fighter groups were assigned to protect Romanian territory. They had older types of fighters, such as IAR-80's, IAR-81's and Bf-109E's. Against unescorted bombers they performed quite well, particularly the IAR-81C's, who were often mistakenly identified by American crews as FW-190's. The commander of the 6th Fighter Group remembered after the war that his fighters had claimed 13 American bombers ( all confirmed ) shot down during the raids on the 4th and 5th of April alone.

However, it was a different story when the Romanian fighters had to face the P-38 Lightning or the mighty P-51 Mustang. At lower to medium altitudes the IAR-81's still stood some chances against the Lightnings, and managed to shoot down some P-38's, but they were totally outperformed by the Mustangs. Just one P-51 was ever claimed by an IAR pilot throughout the entire campaign, on the 28th of June, when adjutant Zisu Sava of the 1st Fighter Group claimed a Mustang, but it couldn't be confirmed and remained a probable. One major success for the IAR-81's came on the 10th of June 1944, when 100 P-38 Lightnings sent to strafe the Popesti-Leordeni airfield were engaged by the 6th Fighter Group. The Americans were taken completely by surprise as they approached their target at 50 meters, and the Romanian pilots jumped them, claiming 23 P-38's shot down ( 14 were confirmed ) for the loss of just 3 IAR's. But from here on the bombers they had to stop kept flying high, at 7000 to 9000 meters, so the IAR's had to climb to those altitudes, where their old K14 engine simply couldn't find enough air to operate properly. Therefore, the two elite groups equipped with Bf-109G's ( the 7th and the 9th ) were brought back from the east front to even the odds a bit. But there were still not even nearly enough fighters to meet the Americans in anything like equal numbers: only 30 to 40 Romanian Bf-109G's, 60 German Bf-109G's and 40 FW-190F's, and finally 80 to 100 IAR-80 or IAR-81's. The Bf-109G was an excellent aircraft, but the P-51, thanks to its Merlin engine equipped with a two-stage compressor, still outclassed it in dogfights over 7000 meters, and most engagements took place at these altitudes. Eventually, all IAR fighters were withdrawn from the home front and sent to the east front, where they could still fight the Soviet airforce on more equal terms. Their brave pilots had claimed close 100 American bombers shot down ( confirmed victories ) during those bloody summer battles.

After the first few weeks of battle, the Luftwaffe attempted to give more depth to the defense, by devising the so called "Sternflug" plan. It called for the concentration of all available fighters on a couple of airfields, after which they would take off and engage the Americans. The Bf-109G's were supposed to go after the fighters, while the 3 German groups equipped with FW-190's ( actually these were ground-attack versions ) would attack the bombers. It looked good on paper, but it didn't work as it was supposed to. German ground controller did their best, but the sheer numbers of American fighters made such precise timing all but impossible. Often, 10 to 30 Romanian or German Bf-109's had to face 200 or more B-24's and B-17's, escorted by 100 or 200 Mustangs or Lightnings. In such condition, it is almost unbelievable they still managed to shoot down some bombers, and that together with the AA artillery, inflicted heavy losses on the Americans.

There was heavy fighting on the east front as well. By July 1944, the Red Army had reached Romania's pre-war borders and there seemed to be no way of stopping the Soviet onslaught. In preparation for their great summer offensive, the Russians grouped the 5th and 17th Air Armies against the ARR and Luftflotte IV. Between them , the Soviet armies could call upon over 1925 fighters and bombers, which gave them a 2.5 to 1 numerical superiority. On the 20th of August 1944, the Soviets unleashed their massive offensive against the Romanian army in the Iasi-Chisinau front. In just three days they managed to overrun most of the units opposing them. The ARR flew many sorties during this period in support of Romanian and German ground forces ( 6 sorties per day for fighters and 4 sorties per day for bombers ). The Red Army took heavy losses from these attacks, but this didn't stop the Russian tanks. Finally, Romania was forced to accept the situation and sign a truce with the Allies on the 23rd of August 1944, bringing the ARR's fourth campaign to an end.

In 4 and a half month of bitter fighting, ARR's fighter squadrons and the 15th USAF clashed in 1487 air battles during the 42 American air raids. A total of 223 B-24 'Liberators' and B-17 'Flying Fortresses' were shot down . 50 American fighters were also shot down ( 29 in air engagements, 20 destroyed by AA fire and 1 more crashed ). Total losses stood at close to 7% of all American forces engaged in combat, which is almost twice as high as losses taken by the 8th USAAF in its raids over Germany, though the 8th USAAF had to spend more time over enemy territory and faced far more enemy fighters. This number alone shows just how powerful were the defenses and how bravely did the Romanian pilots and AA gunners fought. The RAF squadrons who attacked by night lost 48 bombers shot down by night fighters or by AA artillery. ARR and Lufwaffe losses stood at 225 planes shot down or destroyed on the ground ( 80 of them were Romanian fighters) . On the east front, about 110 Soviet planes were destroyed for the loss of just 25 Romanian airplanes. American losses seem to have been higher, as the figure of 223 bombers and 46 fighters includes only the kills confirmed by wrecks found on the ground, but many more planes crashed into the Adriatic Sea or on the territory of other countries. Some sources put the losses as high as 325 bombers and 65 fighters.

Human losses were also heavy on all sides. Over 2200 American airmen were killed or wounded in action. The ARR lost about 60 pilots, including many of its aces ( who were either killed or badly injured ), like captain Alexandru Serbanescu ( 45 kills, KIA on the 18th of August 1944), adjutant Florian Budu, the highest scoring IAR-80 ace ( 16 kills, KIA on the 31st of May ), captain Gheorghe Popescu-Ciocanel ( 12 kills ), adjutant Constantin Lungulescu ( 12 kills ), lieutenant Teodor Greceanu ( 20 kills ), and many others. The Luftwaffe suffered similar ( if not worse ) losses. For example, on the 31st of July alone, 19 German fighters were shot down by the Mustangs. One of the German fighter groups was lead by Helmut Lipfert, one of the greatest Luftwaffe aces ( he had 126 kills in June 1944, when he came to Romania, and 203 kills at the end of the war ). Yet, during his three months tour, Lipfert scored no more than three confirmed kills. In his memoirs, there is a chapter called Rummanischer Sommer ( Romanian Summer ), in which he says : " On the 11th of June 1944, things started to get serious. The Americans sent many airplanes to Ploiesti to bomb the refineries. We moved with 16 aircraft to Zilistea, refueled and took-off again. Thanks to excellent ground control, we were directed towards the enemy formations and immediately made contact with the "big buses". It was a different story... What a huge number of airplanes was present !... Above them, up to 10000 meters, the skies were swarming with enemy fighters, so many of them that I didn't ever dear to look up. After all, what could we do against such a force ?".

The home defense campaign was without doubt the most difficult of all. The ARR had to fight on two fronts simultaneously, facing the Soviet airforce in the east and the mighty 15th USAF over the home soil. Romanian pilots and fought heroically and often gave worse then they got, but in the end they were overwhelmed by sheer weight of numbers. Fortunately for Romania, the country left the Axis on the 23rd of August 1944, before Romanian cities shared the fate of Dresda or Hamburg. Civilian casualties were heavy nonetheless : 15140 civilians were killed and injured. As the campaign suddenly ended on the 23rd of August, ARR squadrons had to hastily regroup and prepare to engage their former allies ( Germany and Hungary ), as the last campaign of the war was about to begin.