The basic principle behind radar is fairly simple. The radar sends out a pulse of radio waves, some of which bounce off of whatever happens to be in their path. These reflections are picked up by the radar and used to build a picture of whatever happens to be out there. But this simplicity masks deep complexity, as various portions of this are implemented in different ways, and even from the earliest days of radar at sea, ships carried multiple sets optimized for different missions.¹

The first USN at-sea radar test aboard the USS Leary, 1937

The first radars, as developed in the late 1930s, were extremely crude. A transmitter would send out a short pulse through an antenna shaped to focus the signal in a particular direction, and then switch over to listening for the echos through the same antenna.² The returned signal would be displayed using a device known as an A-scope, a special cathode ray tube. Essentially, the A-scope would draw a horizontal line for each pulse, deflected up (or down) depending on the received signal strength at a given range as measured by the round trip speed-of-light delay. An object reflecting the beam would appear as a spike or trough on the line, depending on how the A-scope was set up. This gave the operator precise knowledge of ranges, a vast improvement over previous methods, but only in the direction the antenna was pointing. Checking different bearings required rotating the antenna, often manually, and left the operator with the job of keeping track of what was going on around him. This didn't make it impossible to use radar data to build a picture, as the British did with the Chain Home radar feeding information to the Dowding system, but this took lots of manpower and organization. Read more...

In the 1990s, the US Navy found itself at a loose end, as the missions that had defined the late Cold War faded in importance and it reoriented itself towards land attack. The main result was a new destroyer, designed primarily to provide fire support for troops ashore, but with some multi-mission capability. Unfortunately, they decided that this class would be truly stealthy, which drove up size and trapped the ships in a spiral of increasing cost and falling numbers, with a 32-ship program being cut to only three ships by 2008, and coming close to being shut down in 2010 thanks to the resulting cost increases.

USS Michael Monsoor

The first ship, USS Zumwalt (DDG-1000)³ was ordered in 2008, and followed by Michael Monsoor, named for a SEAL killed in Iraq, and Lyndon B Johnson, named for an obscure naval officer who served briefly in WWII. The three ships were laid down in 2011, 2013 and 2017 respectively, but the start of construction did little to slow the cost growth, as the combined procurement cost of the three ships rose from $9 billion in FY09 to $13.3 billion in FY21, not counting R&D costs of something like $10 billion.⁴ The program's weirdness continued as the ships neared completion. Instead of integrating the weapons and then accepting and commissioning the ships, the first two units were officially commissioned in 2016 and 2019, and then sent to San Diego for weapons integration. Zumwalt finally completed this process in 2020, although initial operational capability has continued to slide, and is currently scheduled for Q4 2024. Read more...

The largest surface warships in the American inventory are the three destroyers of the Zumwalt class. These ships are undoubtedly among the most futuristic-looking on the seas, but many have questioned their utility, thanks to the program's troubled history, and the fact that the mission they were built for stopped making sense a decade or so ago.

USS Zumwalt

The Zumwalts, much like the Littoral Combat Ship, dates back to the 1990s, when the US Navy was attempting to define itself in the post-Cold War world. The mission it had built itself around for the previous 40 years, facing down the Soviets at sea, was gone, and it turned instead to the job of influencing events on land. A cheap ship optimized for land attack seemed like a good complement to the multi-role Burkes and Ticonderogas, particularly as it could be fitted with a new gun that would give at least a partial replacement for the capabilities of the recently-retired battleships. Read more...

On April 9th, 1940, Hitler unleashed his forces on Norway and Denmark, hoping to preempt Allied moves into Scandinavia. The plan was to land troops in several strategic cities, using the warships of the Kriegsmarine as transports. The assumption was that the Norwegians would put up at most token resistance, allowing the Germans to get ashore easily, but this was dramatically disproved at Oslo. The force there, led by the heavy cruiser Blucher, managed to get past the outer defenses, but the commander of the inner defenses at Oscarsborg chose to fire, sinking the cruiser with his guns and torpedoes.

HNoMS Olav Tryggvason

But even as Blucher burned, ultimately rolling over and leaving much of the invasion force scattered on the shores of the Oslofjord, the other German ships continued to carry out their mission, some of them having split off before the main force reached the Drobak Narrows and Blucher fell victim to Oscarsborg. One of these was the detachment sent to seize the main naval base at Horten, in the outer reaches of the fjord. It was composed of two torpedo boats, Kondor and Albatros, fast minesweepers R17 and R21, and auxiliary Rau VII. Horten was the headquarters for the defense district protecting Oslo, but the guns intended to guard it were not manned, and its only real protection was the minelayer Olav Tryggvason, recently released from overhaul, and minesweeper Rauma. The German vanguard came in aboard the minesweepers as dawn was breaking, taking the Norwegians, who thought they'd have more warning from their ships patrolling offshore, by surprise. R17 managed to get all the way to the pier before Olav Tryggvason opened fire, the 70 or so men aboard her capturing a pair of Norwegian AA machine guns before the minelayer started pumping shells into the German ship. Three hits left her completely ablaze, and she sank when the fire reached her depth charges. Read more...

Nothing particular to say for this week's open thread (beyond the usual rules still being in effect), but I am very much looking forward to seeing those who are going to be coming to the Iowa meetup tomorrow. I'll be wearing a bright green hat with the Naval Gazing logo on it.

Also, it seems likely that the East Coast meetup this year is going to be in DC instead of Philadelphia to coincide with the DSL meetup. I'd like to do the Museum of the US Navy, but that's on Washington Navy Yard, so getting in on a weekend doesn't seem feasible. Any suggestions?

2018 overhauls are Rangefinding, So You Want to Build a Modern Navy - Aviation Part 2, The Great White Fleet Part 1, The Newport Conference and the US Dreadnought, my review of Batfish and Falklands Part 4. 2019 overhauls are Information, Communication and Naval Warfare Part 3, dndnrsn's review of Bavarian military museums, Rangekeeping Part 2, Impressment, my review of the National WWI Museum and Signalling Part 1. 2020 overhauls are the Goat Locker picture post, Coastal Defenses Part 4, The Pearl Harbor Rant and Mike Kozlowski's review of Fort Monroe.

On the night of April 8th, 1940, the population of Norway slept soundly, unaware that the might of Hitler's war machine was poised to crash on their shores. Warships loaded with troops were just off the country's major cities, hoping to seize them with minimal opposition thanks to the low readiness of Norway's military. The official justification for the German operation was the Allied mining of Norwegian coastal waters to stop the flow of iron ore out of the port of Narvik, although the first German ships sailed before the British did.

Blucher on the way to Oslo

The main target of the German invasion was the capital, Oslo, which would be taken by 2,600 troops carried aboard the brand-new heavy cruiser Blucher, "pocket battleship" Lutzow, light cruiser Emden and three torpedo boats, Albatros, Mowe and Kondor, joined by a batch of R-boat minesweepers. They had sailed from Kiel early that morning, as they had by far the shortest distance of the various forces to go, although the passage wasn't entirely smooth. While transiting the Kattegat, torpedoes were spotted and successfully dodged. They came from the British submarine Triton, which quickly reported their presence to the Admiralty. More submarines were sent into the area, but none were able to attack before the Germans reached the Oslofjord, the long inlet that leads to the city. Read more...

WWI was a war of artillery, and all of the powers involved quickly discovered that they were short on heavy guns. The easiest way to plug this shortfall was to turn to the existing sources of large-caliber artillery, naval and coastal defense weapons. As these were not designed to be mobile, the only real option was to use the best way of moving heavy cargo around, the railways.

USN 14"/50 Railway Gun

The majority of these guns were manned by crews taken from the units that would normally have operated them, and ranged in size from 6" to as much as 15". Because they were made from second-hand guns, a vast array of types were built, most in relatively small numbers. The British made extensive use of their standard 9.2" gun, long a mainstay of coastal defenses, while the US rushed to fabricate railway carriages for a variety of weapons, including almost a hundred 12" mortars from Endicot-period batteries, as well as 8", 10" and 12" guns from the same era. Only a handful made it overseas before the end of the war, and the story of American railway artillery was instead dominated by five USN 14"/50 naval guns mounted on railway carriages that spent two months in action during the closing days of the war. Read more...

The Soviet Union was not alone in looking at building battleships after WWII. The US and Britain both also took looks of varying seriousness during and after the war, drawing on their combat experience to fix the problems of the wartime battleships. The common thread throughout these designs would be an increased focus on the threat from airplanes instead of other battleships.

The final Montana design

Formal US design studies ended in mid-1942, and looked at variations on the basic Montana class, with thicker decks and better AA arrangements. The need for protective decks was seen as particularly acute early in the war, before it became obvious how difficult it was to hit a moving target from high altitude, and the Bureau of Ships looked at reducing the belt to Iowa thickness in exchange for increasing the total deck thickness from 9.24" (equivalent to a single thickness of 7.3" when the different layers were taken into account) to 10.4" (equivalent to 8.3"). This new deck would be enough to keep the US 14" AP bomb out if dropped from anywhere below 19,000'. Other sketches were prepared that accepted a reduction in speed in exchange for an increased AA armament, with better sky arcs than that planned in the existing sketches. By the standards of 1944, even the increased AA armament seemed hilariously lacking, with 16 5"/54s, eight twin Bofors and 24 Oerlikons. One all-machine gun design was even considered, apparently a result of fleet dissatisfaction with heavy AA fire control early in the war, although no details seem to have survived. Read more...

One of the problems that had to be solved when missiles first went to sea was how to carry and launch weapons that were not only bigger and heavier than anything that had previously been carried aboard, but also fragile and complicated, and which had to be fired in quick succession. To make matters worse, each ship could carry only a limited number of missiles, so provisions were also needed for replenishing weapons at sea.

USS Oklahoma City showing her Talos launcher and radars

As the Terrier and Talos missiles had separate boosters, the initial plan was to store the majority of the missiles broken down to fit as many as possible aboard. The problem was that this would sharply limit the rate of fire after the ready-service missiles had been expended, and it soon became clear that the missiles could generally be stored assembled. To shrink the space required, they would be stored without fins, which only took 15 seconds or so to install by a dedicated crew in the last space before the missile was rammed onto the launcher. This wasn't likely to be a serious limitation on the firing rate, as each missile or salvo required a dedicated illuminator throughout its flight. But that still left the question of how to store and transport the missiles, and the Navy came up with a number of different solutions, many of which were installed on various ships. Read more...

It's time as usual for our biweekly open thread. Talk about whatever you want, so long as it's not culture war.

I have a book recommendation for you this time. On Yankee Station is an account of the naval air war in Vietnam, and it's a splendid mix of personal anecdote, clear historical analysis and tactical primer. It's probably going to be my first recommendation for an indictment of the conduct of the war, particularly as it's relatively short and very well-written.

2018 overhauls are Pungdo, So You Want to Build a Modern Navy - Aviation Part 1, Jackie Fisher, Battlecruisers Part 2, Did Iowa Move Sideways During a Broadside? and Auxiliaries Part 2. 2019 overhauls are Soviet Battleships Part 1, Alexander's review of the Newark Air Museum, Battleship Aviation Part 4, Lord Nelson's review of Soya, The Scuttling of the High Seas Fleet and The Blockade of Santiago. And 2020 overhauls are Merchant Ships - Specialized Tankers and Cargo Ships, Naval Rations Part 1 and Tom Clancy.