The Brenner Pass

Among Koplitz's missions with the 340th Bomb Group's 489th Squadron were repeated runs over the Brenner Pass, the Alpine corridor carrying the rail line between Italy and Austria that the Wehrmacht depended on to supply and reinforce its forces in Italy. Allied planners considered it one of the most heavily defended stretches of airspace in the entire Mediterranean theater, ringed with concentrated German anti-aircraft batteries dug into the surrounding mountainsides.

The account below of that campaign — what the men who flew it called the Battle of the Brenner — is by Frank B. Dean, originally published on the Koplitz family's earlier website devoted to the war record, and lightly edited here for spelling and punctuation.

Operation Bingo: Closing the Brenner

On 6 November 1944, the Germans were holding the high ridges in the northern Apennine Mountains they called the Gothic Line. This defense line ran through the mountain ranges that reached, almost unbroken, from La Spezia on the northwest coast of Italy to the city of Rimini on the Adriatic. Near the center, and behind the German lines, was the important transportation center of Bologna. Rail lines bringing war supplies from Germany were, for the most part, routed through the Brenner Pass. Other rail lines from Austria were farther east and led south into Venice and then into Bologna. These were the two main transportation lines that fueled the German war machine in Italy.

It was estimated that 24,000 tons of supplies were flowing to German troops each day — five times the minimum daily requirement needed to support German forces locked in a winter stalemate with Allied troops.

On 6 November 1944, Operation Bingo was put into effect. Its objective was to stop the flow of German supplies to the fighting front by closing the Brenner Pass. The four B-25 bomb groups of the 57th Bomb Wing were to carry the bulk of the load, with fighter-bombers of the 12th Air Force's Tactical Air Command and the British Desert Air Force assisting, and some support from B-17s and B-24s of the 15th Air Force.

The plan rested on electricity. If power could be denied to the electric locomotives used on the pass's steeper grades, the Germans would be forced onto slower, less efficient steam locomotives — which would in turn require diverting effort toward supplying coal for those trains and pulling locomotives and rolling stock away from their existing duties. It was estimated this could reduce the Brenner Pass's carrying capacity to around 10,000 tons a day.

On 6 November, B-25s struck the electrical transformer stations that powered the line: San Ambrogio (hit by the 310th), Ala (hit by the 321st), and Trento (hit by the 340th). All three targets were hit and damaged badly enough to deny electrical power to trains as far north as Bolzano. The 319th, newly converted from B-26s to B-25s, hit railroad bridges at the lower end of the pass.

The German Defenses

Defending the pass initially fell to the 2nd Fighter Group of the Italian Fascist Republic's air force — Italian pilots flying Me-109s under German markings. With only about 50 aircraft, they were never going to be an effective deterrent. The real defense came from the German 5th and 127th Flak Regiments, which between them manned 366 heavy anti-aircraft guns stationed from Verona in the south to Innsbruck in the north. By the end of the first day, more heavy guns had moved in around Ala and Rovereto.

Italian gunners still fought alongside the Germans, though the batteries themselves were manned independently by one nationality or the other — Italian crews using Italian cannon paired with German radar.

The Germans' primary weapon was the 8.8cm Fliegerabwehrkanone — the "88," shortened simply to Flak. It fired a 9.24-kilogram (20.34-pound) shell to well over 49,000 feet, and was paired with the Kommandogerät 40 (KG 40) gun director and 41D gun-laying radar. The gun director was a mechanical calculator with a built-in stereoscopic height finder, capable of predicting a straight or curving flight path; the radar supplied azimuth, angular height, and range. Batteries usually tracked range by radar and direction optically, falling back to radar-controlled or barrage fire — less accurate than visual sighting — when cloud or smoke obscured the bomber formations.

Other guns joined the defense too: Italian 90mm cannon reaching 26,000 feet and 102mm cannon reaching 40,000 feet guarded Brenner Pass targets alongside the German artillery. While the heaviest guns were needed to reach high-flying B-17s and B-24s, lighter pieces — the German and Italian 37mm, effective to 15,000 feet, and the Italian 75mm, effective to 27,000 feet — were all that was needed against B-25s, which rarely flew above 13,000 feet. In practice, that meant any gun from 37mm on up could reach the medium bombers' altitude. Combat crew reports made clear that they all did.

Escalation Through the Winter

As the campaign against the Brenner's rail and road bridges, tracks, and fills continued, so did the number of flak guns. Batteries were added as far north as Bressanone. On 11 November, one flight of B-25s alone had 18 aircraft holed and lost one to a crash caused by flak damage. Of 16 attacks flown in November, 11 drew flak; of 300 sorties that month, 20 B-25s were holed and one crashed.

In December, the Germans moved 69 more guns into the Brenner Pass, bringing the total to 435. Anti-flak operations became standard practice across the 57th: fighter-bombers dropped general-purpose bombs while the bombers themselves dropped 20-pound fragmentation bombs and twisted strips of tin foil — chaff, or "window" — meant to confuse the German radar. At the end of December, the 319th Bomb Group flew its last mission over Italy and returned to the United States in January 1945, leaving the 310th, 321st, and 340th as the only medium bomb groups left in the theater.

By January 1945, flak batteries kept growing — more guns at Bressanone and Verona brought the Brenner's total to 475, some positioned as high as 3,000 feet above sea level, with one battery west of Ala reported at 4,100 feet. Anti-flak tactics gained a new wrinkle that month: formations of three B-25s would fly ahead of the main bomber stream dropping chaff and white phosphorus bombs, meant to burn the gun crews and screen the formation behind smoke. Despite that, of the 48 missions (1,250 sorties) flown over the Brenner that month, 39 drew flak — 224 aircraft were holed and five were lost.

In February 1945, as bombers pushed farther into the pass, the German gun batteries shifted from south to north — Trento and Bressanone saw more guns, and new batteries appeared at Lavis and at Brenner itself, pushing the total to 482. It was now rare for a mission not to draw flak, largely thanks to a refined German early-warning system: gun batteries were alerted once a formation came within 200 kilometers of a defended area, and manned once it closed to 80 kilometers, with the battery commander given the formation's approximate course and altitude ahead of time. There were almost no surprise attacks left. That month, 82 missions (1,771 sorties) were flown over the Brenner; 62 drew flak, 14 aircraft were lost, and 305 were holed or damaged despite the anti-flak effort.

In March 1945, the flak batteries grew again, especially in the northern Brenner — 43 new guns brought the total to 525. Of 96 missions flown that month, 58 drew flak; 14 aircraft were lost and 207 were holed or damaged. Even so, much of the Brenner was rendered impassable to German traffic for most of the month.

The Final Offensive

In April 1945, the final Allied assault on the Gothic Line began, and the air effort against the Brenner itself was scaled back to free up aircraft for direct ground support — many guns were pulled out of the pass to protect other targets as the front moved. The 57th Bomb Wing relocated, with its three bomb groups, from Corsica to northeastern Italy to be closer to the fighting.

Even scaled back, the 64 missions flown against Brenner targets in April still mattered — 25 drew flak that holed 87 aircraft and downed five, and together they kept the pass's rail lines effectively cut. Through the final offensive, the B-25s of the 57th spent much of their time hitting troops, guns, pontoon bridges, ferries, and staging areas to keep the Germans from crossing the Po River, while also smashing the rail lines and bridges that might have offered an escape route back to Germany.

The effect of months spent slowly strangling the Brenner Pass only became fully apparent as German forces tried to retreat. Missing bridge spans left retreating troops unable to use the rail lines; shortages of ammunition and gasoline crippled their motor transport and, with it, their ability to fight. On 26 April 1945, the 340th Group flew the last combat mission of the war for the 57th Bomb Wing. Bad weather grounded the medium bombers after that, until German forces signed surrender papers on 29 April 1945, effective 2 May 1945.

The Battle of the Brenner, by the Numbers

From 6 November 1944 to 25 April 1945, the B-25s of the 57th Bomb Wing fought what the men who flew it called the Battle of the Brenner. They flew more than 6,849 sorties against enemy targets in the pass and dropped 10,267 tons of bombs on targets running south to north: Verona, Domegliara, San Ambrogio, Volargne, Ceraino, Dolcè, Peri, Ossenigo, Vo Sinistro, Ala, San Margherita, Mori, Rovereto, Calliano, Aldeno, Trento, San Felice, San Michele, Lavis, Salorno, Ora, Bronzolo, Ponte all'Isarco, Bressanone, La Cave, Campo, Vipiteno, Colle Isarco, and Brennero — ranging beyond Italy to bomb Austrian bridges at Steinach and Matrei as well.

A handful of place names in that list were corrected against the known geography of the Adige valley rail line (e.g. "Bolargne" to Volargne, "Solorno" to Salorno) — worth checking against the original page if exact fidelity to the source text matters.

The battle was not without cost. In that short span, 46 B-25s were lost (two to enemy fighters) and 532 more were damaged by flak. From 2 January 1945 alone, ten men were killed and 131 were listed as missing in action; ninety-two more were wounded, twelve of them critically — 223 casualties in all from the 57th. Had the B-25 not been the exceptionally sturdy aircraft it was, the losses would have been far higher.

There was the one great war everyone knew about. Within it were smaller wars that generated plenty of killing but little publicity — and smaller wars still, known only to the men who fought them. One of these was "the Battle of the Brenner," fought between American combat crews flying B-25 bombers in the sky and German and Italian anti-aircraft crews on the ground. It was little noted or long remembered, except by those who fought there. It had been mean and brutal while it lasted.

In the end, those who survived came home; some never did, and some returned from prison camps instead. The wounded carried their scars. The dead stayed dead, mourned only by those who knew them. Then, as time passed, there came a time for remembering — even after time had dulled the memory and scattered the log books — and someone went looking through what scanty record remained, trying to write enough to stir some old, dormant memories.

This is one such story, written for those who flew in twin-tailed bombers and watched the red or black bursts of flak fill the sky over the Brenner Pass in late 1944 and early 1945.

The original page closed with Randall Jarrell's short 1945 poem "The Death of the Ball Turret Gunner." It's still under copyright, so it isn't reproduced here — but it's worth finding in any anthology of WWII poetry; it distills the same arithmetic of miles flown, guns fired, and men lost that runs through the numbers above.

Flying a B-25 Mitchell into that kind of concentrated flak, low and relatively slow compared to a fighter, was among the more dangerous work a medium-bomber crew could draw in the Italian campaign. It was against this backdrop that Koplitz's combat record climbed past 70 missions — and that his skill as a pilot marked him, later, for test pilot duty.