The Baltimore was a direct evolution of the Martin Maryland (Model 167), a fast twin-engined attack bomber that Martin had originally offered to the US Army in the late 1930s. The Army passed on it, but France and then Britain bought the Maryland eagerly, valuing its speed. In service, though, crews found it cramped and light on bomb load, and both customers asked Martin for something with more power and a bigger punch.

Martin’s response, the Model 187 Baltimore, kept the Maryland’s basic layout but deepened the fuselage, fitted more powerful Wright Twin Cyclone radials, and strengthened the airframe to carry more bombs and heavier defensive armament. The result looked like a beefed-up Maryland — which is essentially what it was. The lineage matters: the Baltimore was not a clean-sheet aircraft but the refinement of a design already proven, if imperfectly, in French and British hands.

Before the United States entered the war, Britain and France bought large quantities of American aircraft through a joint body, the Anglo-French Purchasing Commission, paying cash for machines their own industries could not produce fast enough. The Baltimore was ordered under this arrangement in 1940. When France collapsed in June 1940, the French share of the order was taken over by Britain, and every subsequent Baltimore was built for the RAF.

The naming followed a British habit: American aircraft in RAF service were often christened after US places or given British-sounding names. Martin’s bombers became the Maryland and the Baltimore, both named for the company’s home state and city. The US Army Air Forces later applied its own label, A-30, and accepted a small number, but the Baltimore was overwhelmingly a British and Commonwealth aircraft in everything but manufacture — a product of Lend-Lease and cash-and-carry rather than American operational need.

The single most discussed feature of the Baltimore among its crews was the fuselage. To keep drag low and speed high, Martin gave the aircraft a body that was deep from top to bottom but strikingly narrow from side to side. The four crew members — pilot, navigator/bomb-aimer, and two gunners — each had their own compartment, but the narrowness meant those compartments were effectively sealed off from one another.

In practice this meant no crew member could move to another’s station in flight. If the pilot were killed or badly wounded, nobody could reach the controls to fly the aircraft home. If a gunner were hit, no one could give first aid. On other bombers a crew could redistribute itself in an emergency; on the Baltimore it could not. It was a genuine weakness, accepted in the name of performance, and it coloured the type’s reputation for the rest of its career — a reminder that an aircraft’s worst feature is sometimes the price of its best one.

The Baltimore’s natural home was the Desert Air Force, the tactical air command that supported the British Eighth Army in North Africa and later up through Sicily and Italy. Baltimores flew as medium-altitude day bombers, typically in tight boxes of a dozen or more aircraft with a strong fighter escort, striking airfields, ports, marshalling yards, supply dumps, gun positions and columns of vehicles.

This was the unglamorous grind of tactical air power: repeated, methodical strikes to wear down an enemy’s ability to move and supply his forces. The Baltimore suited it well. It was fast enough to make interception difficult, accurate enough in the bombing role thanks to its good visibility, and rugged enough to absorb damage. Alongside the Douglas Boston and other types, it helped give the Desert Air Force the relentless offensive tempo that ground down Axis logistics in the Mediterranean.

The Baltimore was powered by two Wright GR-2600 Twin Cyclone fourteen-cylinder radials, the same well-regarded family of engines that powered the B-25 Mitchell and many other American types. Early marks used versions of around 1,600 horsepower each; later marks fitted more powerful variants, pushing the top speed to roughly 490 km/h (about 305 mph) — genuinely fast for a light bomber of its day.

That speed was the Baltimore’s headline virtue. It let the type run in and out of a target area quickly, complicated the job of enemy fighters, and gave crews a real chance of outpacing trouble on the way home. Range and bomb load were modest by heavy-bomber standards — the Baltimore was a tactical machine, not a strategic one — but for hitting targets a few hundred kilometres behind the front line, several times a day, its combination of speed and reliability was exactly right.

One area where the Baltimore steadily improved was self-defence. Where the earlier Maryland had been lightly armed, the Baltimore grew progressively heavier defensive firepower through its marks. Fixed machine guns in the wings gave the pilot a forward strafing capability, and the rear was covered by dorsal and ventral gun positions.

Later marks replaced hand-held dorsal guns with a powered turret, significantly improving the field and weight of fire against fighters attacking from above and behind — the classic bomber-killing approach. Combined with the Baltimore’s speed and rugged structure, this made it a genuinely awkward target. Crews reported that a formation of well-flown Baltimores, guns coordinated, could give attacking fighters a very unpleasant reception, which was no small thing in the contested skies of the Mediterranean.

Few wartime aircraft served under so many national badges at once. The RAF was the principal operator, but the South African Air Force flew several Baltimore squadrons in the Mediterranean and Italy, and Royal Australian Air Force squadrons under RAF command used the type over the Mediterranean and the Balkans. Free French units operated Baltimores as part of the Allied air effort, and Greek squadrons flew them too.

Most strikingly, after Italy surrendered and switched sides in 1943, the Italian Co-Belligerent Air Force — former enemies — received Baltimores and flew them against their old German allies, continuing to operate the type into the post-war years. This multinational service is part of what makes the Baltimore such an unusual aircraft to trace: it belonged fully to no single air force’s story, and so tends to fall through the cracks of national histories.

As with most Lend-Lease and cash-and-carry aircraft of the period, the Baltimore has no clean, reliable published figure for unit cost, cost per flight hour or total programme cost. It was procured through complex wartime financial arrangements between governments rather than sold at a transparent list price, and the surviving records are fragmentary. Any precise dollar figure quoted for it online should be treated with caution.

What can be said is that the Baltimore was a conventional, mass-produced twin built on an established design and engine family, which kept it relatively economical to build and maintain by the standards of the day. It was cheap enough, and available enough, to equip numerous squadrons across several air forces. We list its cost fields as “not reliably recorded” rather than invent numbers that the sources do not support.

One of the more remarkable facts about the Baltimore is that, despite roughly 1,575 being built, no complete example is known to survive anywhere in the world. This is unusual for an aircraft produced in such numbers, and it comes down to a combination of factors: the type fought and was worn out far from home, it was operated by air forces that scrapped it quickly after the war, and it was never adopted as a national icon whose preservation anyone championed.

What does survive are fragments and wreck sites — the remains of aircraft lost over the Mediterranean and elsewhere, some of which have been surveyed by divers and aviation archaeologists. There is periodic interest in recovering and one day reconstructing a Baltimore, but for now the type exists only in photographs, documents, museum components and the seabed. Its total disappearance as a flying or even static airframe is itself a small monument to how completely the tactical workhorses of the war were used up and discarded.

The Baltimore was produced in a series of marks, broadly Mk I through Mk V, that traced a steady increase in power and defensive armament rather than any radical change of shape. Early marks (Mk I–III) established the type in service with hand-operated or lighter dorsal armament; later marks (Mk IIIA, IV and V) introduced a powered dorsal turret and more powerful engines, improving both firepower and performance.

In American nomenclature the turret-equipped, US-built-for-Lend-Lease versions were designated A-30 and A-30A. The differences between marks were evolutionary and cumulative — a bomber being continuously improved in production to keep pace with the tactical air war — rather than distinct new models. For most of its front-line career the Baltimore that mattered was the later, turret-armed, higher-powered version.

The Baltimore belongs to a whole family of American twin-engined bombers that fought in Allied hands during the war, and it helps to place it among them. Its direct ancestor, the Martin Maryland, was smaller, lighter and less heavily armed — the Baltimore was essentially the Maryland grown up. Alongside it in the Mediterranean flew the Douglas Boston (the RAF name for the A-20 Havoc), a broadly comparable light bomber that many crews found roomier and more pleasant, and which is far better remembered today.

Larger still was Martin’s own B-26 Marauder, a fast medium bomber in a different weight class, and the North American B-25 Mitchell, which shared the Baltimore’s Wright Twin Cyclone engines but carried more and flew further. Against these the Baltimore occupied a specific niche: a fast, well-defended light day bomber for tactical work at short-to-medium range. It was not the most capable or the most comfortable of the group, but in the Desert Air Force’s hands it did a particular job efficiently, and it did it in large numbers.

A Baltimore carried a crew of four: the pilot, a navigator/bomb-aimer in the glazed nose, and two gunners in the rear covering the dorsal and ventral positions. Because of the narrow fuselage, each occupied what was effectively a separate compartment, and the four could neither see much of one another nor swap places in the air. It made for an isolating flying experience, especially for the gunners tucked into the rear.

That isolation had real operational consequences. On other bombers a wounded pilot might be pulled from his seat and replaced, or an injured man moved to safety and treated; on the Baltimore, each man was on his own for the duration of the sortie. Crews learned to rely on the aircraft’s speed and armament to keep them out of trouble in the first place, because if trouble arrived, there was very little they could do to help each other. It is a detail that says a great deal about the hard bargains of wartime aircraft design.

With no complete Baltimore left in any museum, what interest survives has turned to wrecks. A number of Baltimores were lost over or into the Mediterranean, and some of these underwater sites have been located and surveyed by divers and aviation archaeologists, offering a rare direct look at the type’s structure. Scattered components — instruments, guns, sections of airframe — also survive in collections.

From time to time there is talk of recovering a Baltimore for preservation or even long-term reconstruction, and the total absence of the type from the world’s museums gives such efforts real appeal. For now, though, the Baltimore remains uniquely absent: an aircraft you can read about and see in hundreds of wartime photographs, but cannot stand in front of anywhere on earth. That absence is part of its story, and part of why it deserves a proper record.