Baltimore-class cruiser

The Baltimore class cruiser (and the three ship Oregon City sub-class) was a type of heavy cruiser in the United States Navy from the last years of the Second World War. Fast and heavily armed, ships like the Baltimore cruisers were mainly used by the Navy in World War II to protect the fast aircraft carriers in carrier battle groups. With their strong anti-aircraft armament, Baltimores could contribute especially in air defenses of these battle groups. Additionally, their 8-inch main guns and smaller medium guns were regularly used to bombard land targets in support of amphibious landings. After the war, only St Paul, Macon, Toledo, Columbus, Bremerton, Helena, Albany, and Rochester remained in service, while the rest were moved to the reserve fleet. All except Boston, Canberra, Chicago and Fall River were reactivated for the Korean War. By 1971, all ships remaining in the original design configuration were decommissioned, and started showing up the scrap-sale lists. However, five Baltimore class cruisers were refitted and converted into some of the first guided missile cruisers in the world, becoming the three Albany-class cruiser and two Boston-class cruiser cruisers. The last of these was decommissioned in 1980, with the Chicago and Albany lasting until 1991 in reserve. No example of the Baltimore class still exists.

Planning and construction
Immediately after the outbreak of World War II in September 1939, the US Navy initiated studies regarding a new class of heavy cruiser, which eventually led to the construction of the Baltimore class. With the start of the war, the limitations instituted by the Second London Naval Treaty, which had completely banned the construction of heavy cruisers, became obsolete. The Baltimore class was based partly on the USS Wichita, a heavy cruiser from 1937, which represented the transition from inter-war to Second-World-War designs. It was also based partly on the Cleveland-class cruiser, a light cruiser that was then being built. In profile the Baltimores looked very much like the Cleveland-class light cruisers, the obvious difference being that the larger Baltimores carried nine 8 in guns in three triple turrets, compared to the 12 6 in guns in four triple turrets of the Clevelands.

The construction of the first four ships of the Baltimore class was began on July 1, 1940 and four more were ordered before the year was out. A second order, which consisted of 16 more ships, was approved on August 7, 1942. The completion of the ships was delayed, because the Navy gave priority to the construction of the lighter Cleveland-class ships, as more of the lighter ships could be completed more quickly for deployment in carrier groups. With the construction of the first eight Baltimore class ships moving slowly, the US Navy used the time to review the initial plans and improve them. The new, modified design was itself delayed, so that construction had begun on a further seven ships--for a total of 15--using the original design before the revisions were completed. The final nine ships ordered were converted to the second, modified design. Between 1943 and 1946, 14 ships of the Baltimore class entered service. Construction of the fifteenth ship, which would have been the Norfolk, was stopped at the end of the war after eight months of work had already been done, and the half-completed hull was scrapped.

The largest contractor for the construction of the Baltimore class ships was Bethlehem Steel, which produced eight ships at the Fore River Shipyard in Quincy, Massachusetts. New York Shipbuilding in Camden, New Jersey built four and the Philadelphia Naval Shipyard in Philadelphia completed one in addition to working on the final, uncompleted ship. The ships were named after cities in the United States, the only exception being the USS Canberra (CA-70), which was named in honor of HMAS Canberra (D33) (sunk at the battle of Savo Island) which had been named after Canberra, the Australian capital. The classification "CA" originally stood for "armored cruiser" but was later used for heavy cruisers.

Service
Of the seventeen completed ships, twelve were launched before the Japanese capitulation on September 2, 1945, though only seven took part in the battles of the Pacific Theater and one in the European Theater. The other ships were still completing their testing in the final days of the war. By 1947, nine of the Baltimores had been decommissioned and placed in the reserve fleet, while seven (Helena, Toledo, Macon, Columbus, St Paul, Rochester, and Albany) remained in service. However, at the start of the 1950s, six were reactivated (Macon had been decommissioned for four short months: June–October 1950), making thirteen available for deployment in the Korean War. Six of these were used for escort missions and coastal bombardment in Korea, while the other seven reinforced fleets in other areas of the globe. The remaining four remained out of service: the Fall River was never reactivated, the Boston and Canberra were refitted as Boston-class guided missile cruisers (CGs), and the Chicago was reactivated after being converted to an Albany-class CG.

After the Korean War, beginning in 1954 with Quincy, some of the Baltimores decommissioned for good. By 1969, six ships were still in commission; four (Boston, Canberra, Chicago, Columbus, Albany) as CGs, and only one unmodified ship, the Saint Paul, which remained active to serve in the Vietnam War, providing gunfire support. St Paul was the longest serving (26 years) member of the class, and was finally decommissioned in 1971. Boston and Canberra retired in 1970, Columbus in 1975, and finally Chicago in 1980. All fourteen of the original Baltimores were sold for scrap after being decommissioned, with Chicago being the final one broken up in 1991.

Damage and Casualties
In World War II, only the Canberra was damaged through enemy fire, when she was struck with a compressed air torpedo on October 13, 1944, which killed 23 men in the engine room and left the ship immobilized. The ship was hit amidships and both boiler rooms were flooded with 3,000 tons of seawater. She was towed away by sister Boston, and as a result both ships missed the crucial Battle of Leyte Gulf. A year later, repairs were completed at the Boston Naval Shipyard and Canberra was assigned to the Atlantic Fleet. In June 1945, the Pittsburgh had her entire bow ripped off in a typhoon, but there were no casualties. The ship struggled through 70 kn winds to Guam, where provisional repairs were made before sailing to the Puget Sound Naval Shipyard for a full reconstruction. Pittsburgh's detached bow stayed afloat, and was later towed into Guam and scrapped.

During the Korean War, a fire in a forward turret on April 12, 1952 killed 30 men on the St Paul. Then, in 1953, the same ship was hit by a coastal battery, though without injury to the crew. The Helena in 1951 and the Los Angeles in 1953 were also struck by coastal batteries without injuries during the war.

In June 1968, the Boston, along with its escort, the Australian destroyer HMAS Hobart (D 39), were victims of friendly fire when planes of the US Air Force mistook them for enemy targets and fired on them with AIM-7 Sparrow missiles. Only Hobart was seriously damaged; although the Boston was hit, the warhead of the missile failed to detonate.

Refittings (Albany and Boston classes)
By the latter half of the 1940s, the navy was planning warships equipped with missiles. In 1946 the battleship USS Mississippi (BB-41) and in 1948 the seaplane tender USS Norton Sound were converted to test this idea. Both were equipped, among other weapons, with RIM-2 Terrier missiles, which were also used after 1952 on the first series of operational missile cruisers. Two Baltimore-class cruisers were refitted in this first series, the USS Boston (CA-69) and the USS Canberra (CA-70). These were the first operational guided missile cruisers in the world. They were designated the Boston-class cruiser and returned to service in 1955 and 1956 respectively, reclassified as CAG-1 and CAG-2--"G" for "guided missile" and maintaining the "A" because they retained their heavy guns.

In the following years six ships of the Cleveland class were equipped with guided missiles and in 1957 the first ship designed from the start to be a missile cruiser was completed (the USS Long Beach (CGN-9)). Ships also continued to be converted, so starting in 1958, two Baltimore-class cruisers, the USS Chicago (CA-136) and the USS Columbus (CA-74), along with an Oregon City-class cruiser, (considered a sub-class of the Baltimore-class) the USS Albany (CA-123), were converted to the new Albany-class cruiser. These were launched in 1962 and 1964, respectively. Two more ships were planned to be refitted as Albanys, the Baltimore-class USS Bremerton (CA-130) and another Oregon City-class cruiser, the USS Rochester (CA-124) but these conversions were cancelled on financial considerations. As opposed to the Boston-class refit, the Albany-class refit required a total reconstruction. Both entire weapons systems and the superstructure were removed and replaced with new ones; the cost of one refit was $175 million. Because no high-caliber weapons were used, the Albany class ships received the designation CG.

Hull
Baltimore-class cruisers were 673 ft long and 70 ft wide. Since the hull was not altered in either the Albany or the Boston class, these numbers were the same for those ships as well, but the alterations differentiated them in all other categories.

Fully loaded, original Baltimores displaced 17031 long ton of water. Their draft was 23 ft. At the bow, the top level of the hull lay 33 ft above the water; at the stern, 25 ft. The funnels were 86 ft high, and the highest point on the masts was at 112 ft. The superstructure occupied about a third of the ship's length and was divided into two deckhouses. The gap between these housed the two thin funnels. Two masts, one a bit forward and the other a bit aft of the funnels, accommodated the positioning electronics.

The vertical belt armor was 6 in thick and the horizontal deck armor was up to 3 in thick. The turrets were also heavily armored, between 3 and 6 in thick, while the command tower had the thickest armor, at 8 in.

The Boston class had a draft about 20 inches (half a meter) deeper in the water, and displaced about 500 long ton more water than their former sister ships. Because the Bostons were only partially refitted, the forward third of the ship remained virtually untouched. The first serious change was the combination of what were two funnels on the Balitmores to just one, thicker funnel, which still stood in the gap between the two deckhouses. Because the missiles required more guiding electronic systems, the forward mast was replaced with a four-legged lattice mast with an enlarged platform. The most conspicuous change was of course the addition of the missile-launching apparatus and its magazine of missiles, which took up the entire back half of the ship and replaced the guns which had been there.

The three Albanys were completely rebuilt from the deck level up, to the point that they bear very little resemblance to their former sister ships. The deckhouse now took up nearly two thirds of the ship's length and was two decks high for almost the entire length. Above that lay the box-shaped bridge which was one of the most recognizable markers of the class. The two masts and funnels were combined into the so-called "macks - a portmanteau word combining "mast" and "stack" (smokestack) - where the electronics platforms were attached to the tops of the funnels rather than attached to masts rising all the way from the deck. The highest points on the forward mack was more than 130 ft above the water line. Such heights could only be achieved with the use of aluminum alloys, which were used to a great extent in the construction of the superstructures.  Despite, this the fully loaded displacement of the Albanys grew to more than 17500 long ton.

Propulsion
The Baltimore cruisers were propelled with steam power. Each ship had four shafts, each with a propeller. The shafts were turned by four steam turbines, the steam produced by four boilers, which at full speed reached pressures of up to 615 psi. The Baltimores each had two engine rooms and two funnels, though this was changed in the Bostons, which only had one funnel for all four turbines, as noted above. The high speed was around 33 kn and the performance of the engine was around 120000 HP.

The original Baltimores could carry up to 2250 long ton of fuel, putting the maximum range at a cruising speed of 15 kn at about 10000 nmi. The increased displacement of the modified Boston and Albany classes meant their range was reduced to about 9000 and 7000 mi respectively, despite increases in fuel capacity to 2600 and 2500 tons.

Armament
The main armament of the Baltimore class consisted of three turrets, each with three Mark 15 8"/55 caliber guns (Mark 12 in Baltimore). Two of these were located forward and one aft. The range of these guns was 17.3 mi. The secondary armament was twelve 5"/38 caliber guns in six twin mounts. Two mounts were located on each side of the superstructure and two were behind the main batteries fore and aft. These guns could be used against aircraft, ships, and for shore bombardment. Their range for surface targets was 10 mi and they could reach airplanes at altitudes of up to 6 mi. In addition, the ships had numerous light anti-aircraft weapons: 12 quadruple mounts of Bofors 40 mm guns (or 11 quadruple mounts and 2 twin mounts on ships with only one rear aircraft crane) as well as 20-28 Oerlikon 20 mm cannon, depending on when a given ship was commissioned. After WW2, the small-caliber weapons were soon removed. The 20mm anti-aircraft guns were removed without replacement shortly after the war due to limited effectiveness against kamikaze attacks, and because it was expected they would be completely ineffective against postwar aircraft. The 40mm Bofors were replaced with 3"/50 caliber guns in the 1950s.

Four ships, the USS Toledo (CA-133), USS Macon (CA-132), USS Helena (CA-75), and USS Los Angeles (CA-135), were also each equipped with three nuclear cruise missiles of the SSM-N-8 Regulus type between 1956 and 1958. Ultimately, though, the deployment of such missiles on surface ships remained an experiment, which was only undertaken until the 1960s. The successor UGM-27 Polaris was carried only by nuclear submarines. In the late 1950s, plans were made to fit Polaris to missile conversions of these cruisers, but the only missile cruiser conversion ever so equipped was the Italian cruiser Giuseppe Garibaldi, (four tubes), and the missiles were never actually shipped.

Electronics
Initially, the Baltimores were equipped with SG radar systems for surface targets and SK systems for airborne targets. The range of these systems for surface targets, depending on the size of the target was between 15 and 22 nmi. The SK could detect bombers at medium altitudes from 100 nmi. The radar systems were replaced in the Korean war with the more effective SPS-6 (built by Westinghouse Electric or later with the SPS-12 (from the Radio Corporation of America combined with a SPS-8 as a height-finder. With these systems the detection range for bombers was increased to 145 mi. The ships in active service longer received further upgrades in their final years: the SPS-6 was replaced with the SPS-37 (also from Westinghouse) and the SPS-12 was replaced with the SPS-10 from Raytheon. With this equipment planes could be detected at over 250 mi away.

The Baltimore-class was equipped from the start with electronic fire control systems to determine the fire-parameters by which targets over the horizon could be hit. The main guns were controlled by a Mark 34 fire control system connected to an MK 8 radar. The AA guns were guided by Mk 37 systems with Mk-4 radar. Later, the fire control radars were replaced along with the main radar systems. The fire control systems remained the same except that the new 3 in guns were fitted upgraded to Mk 56 with Mk 35 radars.

Aircraft
The onboard flight systems of the Baltimore-class cruisers during World War II consisted of two aircraft catapults on the side edges of the aft deck. Between the catapults was a sliding hatchway which was the roof of an onboard hangar. Directly under the hatch was an aircraft elevator. The hangar had room to accommodate up to four aircraft at one time, one to port forward of the elevator, one to port abeam the elevator, one starboard abeam, and one on the elevator itself. The first four ships of the class had two cranes each, while the later models had only one.

At full speed, Vought OS2U Kingfisher could be launched from these catapults and later Curtiss SC-1 Seahawk as well. These planes were used for reconnaissance, anti-submarine, and rescue missions. The planes were seaplanes, and after their missions would land in the water near the cruiser and be lifted back up into the ship by the crane or cranes in the rear and reset upon their catapults. In the 1950s, the catapults and the accompanying capacity to launch airplanes were removed, though the cranes were left and the hangars used to house helicopters, ship's boats or the workings of the Regulus missile system.

The USS Macon (CA-132), in 1948, had a slightly elevated helipad installed instead of the catapults. Because of the helipad, the available firing angles for the main guns were sharply narrowed and the experiment was therefore quickly abandoned and not attempted on any other ships of the class. The ships of the Albany-class did have an area on the deck for helicopters to land, but no platform.

Later designs
The hull of the Baltimore-class was used for the development of a number of other classes. The Oregon City-class cruisers differed only slightly from Baltimores, because they were originally planned as Baltimore-class cruisers but were constructed based on modified plans. Though nine ships were planned, only three were completed. The main differences between the two classes is the reduction to a single-trunked funnel, a redesigned forward superstructure that was placed 40 ft further aft, primarily to decrease top-heaviness and increase the arcs of fire for the guns. A somewhat enlarged design resulted in the Des Moines-class cruiser. While the basic deck layout was unchanged, this class carried the first fully automated high-caliber guns on a warship, though none was constructed in time to take part in World War II.

The plans for the Saipan-class aircraft carrier-light aircraft carrier were adapted from the drafts of the Baltimore hull design, and, for example the layout of the engines was transferred as well. The hulls of these ships were, however, significantly widened. The Saipan-class ships were completed in 1947 and 1948, but by the mid-1950s, they proved too small for the planes of the jet age and were converted for use as communication and command ships.

Crew
The size of the crew of a Baltimore-class cruiser varied by era and by tactical situation. Different sources also differ about the numbers. Naturally, the crew sizes were larger during wartime and furthermore, some cruisers—including all three of the modified Albany-class—were used as flagships and therefore housed an admiral and his staff.

At launch, during and shortly after the war, the crews consisted of around 60 officers and about 1000 rank and file crewmen. When an admiral's staff was aboard during wartime, this number could swell to 80 officers and 1500 crewmen. On the Bostons, the standard crew, even in peacetime and without an admiral's staff, was 80 officers and around 1650 crewmen. Because the Albany-class was equipped almost exclusively for guided-missiles, it required fewer crew than the Bostons, and was roughly comparable numerically to the basic Baltimore.

Compared to today's crew sizes, these numbers seem high. The modern Ticonderoga-class cruiser is manned by about 400, a sign of the advances of automation and computerization on warships through the Navy's Smart Ship program.

Quarters for the crew lay mostly below deck as the superstructure was the site of the Combat Information Center (CIC) and possibly the Admiral's headquarters.

Ships in class

 * USS Baltimore (CA-68)
 * USS Boston (CA-69, CAG-1)
 * USS Canberra (CA-70, CAG-2)
 * USS Quincy (CA-71)
 * USS Pittsburgh (CA-72)
 * USS Saint Paul (CA-73)
 * USS Columbus (CA-74, CG-12)
 * USS Helena (CA-75)
 * USS Bremerton (CA-130)
 * USS Fall River (CA-131)
 * USS Macon (CA-132)
 * USS Toledo (CA-133)
 * USS Los Angeles (CA-135)
 * USS Chicago (CA-136, CG-11)