Quote of the Day
If you want real joy, stop looking at yourself and see how you can help someone else.
— Luke Mickelson (2018 CNN Hero). I have found the Benedictine principles of hospitality, stewardship, and service are key to my own happiness and sense of purpose. In particular, the focus of the Benedictines on having an attitude of gratitude is particularly important. This all meshes well with my stoic approach to life.
I have been working through the book Collect, Combine and Transform Data Using Power Query in Excel and Power BI by Gil Raviv – it is an excellent Power Query (PQ) resource. I particularly like the methods discussed in Chapter 10, which focused on how to make your queries robust, that is, insensitive to minor deviations in the input data. Chapter 10 spoke to me, and I immediately began looking for some practice data that suffered from common inconsistencies: headings in different cases, minor spelling errors in the data body, and inconsistent wording (example, "Co." instead of "Company"). I found that data in the Wikipedia's information on US WW2 cruisers. In this post, I will look at the production of cruisers by the US during WW2. See Figure 1 for a typical example of a WW2 US light cruiser.
For those who are interested, my workbook is here.
Gil presents a number of methods that I applied in this exercise:
- Use standard PQ functions to ensure the headings were all in the lower, upper, or proper cases.
- Create custom functions for processing files using a template file as the basis for your work.
- Setup conversion tables that contain all the inconsistencies present in your data set and the consistent value you want to use. Merging will be used to perform the replacements.
My analysis approach was straightforward:
- Grab the URLs of the Wikipedia pages with the cruiser data I wanted.
- Tidy the data from one of those pages in a way that will work with all other pages (the hard part).
- Make a function of that template.
- Apply the function to all the different URLs.
- Aggregate the data using pivot tables.
- Plot what needs to be plotted.
What is a Cruiser?
I like this definition of a cruiser that I found on the GlobalSecurity.Org website.
By the mid-20th Century, cruisers were medium-sized, general-utility ships. They had a large cruising range and are capable of high speeds (over 30 knots). They served as protective screens against surface and air attacks and also provide gunfire support for land operations. Cruisers were lightly armored, heavily armed, fast ships designed to screen formations and to scout out enemy fleets. Their survivability depended on speed, not armor. This continued to be the meaning until after the Second World War - a fast, long-range, lightly armored ship, although by then more powerful than a destroyer.
Cruisers were further subdivided into three types:
- Light Cruiser
- For the US Navy under treaty limits, light cruisers mounted 6-inch main guns and had displacements of less than 10,000 tons.
- Heavy Cruiser
- For the US Navy under treaty limits, heavy cruisers mounted 8-inch main guns and had displacements of ~10,000 tons. Anything larger in terms of guns and displacement would have had them considered capital ships and subject to stringent naval arms control treaty regulations. After WW2, the US increased the displacement for heavy cruisers to 17,000 tons with the commissioning of the Des Moines-class.
- This class of ship was poorly defined. They were similar in displacement, armament, and cost to battleships, but differed slightly in form and balance of attributes. Battlecruisers typically carried slightly thinner armor and a lighter main gun battery than contemporary battleships, installed on a longer hull with much higher engine power to attain faster speeds. For the US Navy, battlecruisers carried 12-inch main guns. The Alaska-class was comparable to the German's Scharnhorst-class battleships, which carried 11-inch guns. (Wikipedia)
The cruiser mission changed throughout WW2. Early in the war, cruisers played a crucial surface combat role (for example, see the Battle of Savo Island). As the Imperial Japanese Navy's surface fleet became a shadow of its former self, US cruisers finished the war with carrier air defense and land bombardment as their key roles.
I am basing my work here on the Wikipedia's list of US WW2-era cruisers. The Wikipedia list includes all cruisers that served in WW2 or were in construction during the conflict (Figure 2), which means that it includes some obsolete classes (example: Omaha-class) and some that were not commissioned until after the war (example: Juneau and Fargo-classes).
US Cruisers Commissioned During WW2
Between the attack on Pearl Harbor (7-Dec-41) and VJ Day (2-Nov-45), the US commissioned 47 cruisers in 4 different classes. Figures 3(a) and 3(b) show that most of the cruisers commissioned were light cruisers.
|Figure 3(a): Number of US Light, Heavy, and Battle Cruisers Commissioned that Served During WW2.||Figure 3(b): US Cruiser Classes Commissioned During WW2.|
The Alaska-class battlecruisers were the bruisers of the bunch but came so late in the war that they had little impact. The reason the Alaska-class was so late was it was a new class with a new gun, and it just takes time to work through the teething problems. In other posts, I have applauded those US war planners that focused on producing war material that could be delivered to the front in time to make a difference – the Liberty ship and M4 Sherman tank are cases in point. The Alaska-class example should serve as a warning to those who are not careful about managing risk during development. For interesting forum discussions on the Alaska-class ships, look here and here.
US Rate of Cruiser Commissioning During WW2
Figure 4 shows the rate of the US cruiser commissioning during WW2. The US had been ramping up warship production starting in 1940 with the Two-Ocean Navy Act, which authorized the adding 257 ships to the US Navy. After the Pearl Harbor attack, warship production accelerated even further. However, warships take a long time to build. Figure 4 shows that the cruiser commissioning rate did not significantly increase for two years after Pearl Harbor.
Figure 5 shows the US shipyards tasked with building the new cruisers. These shipyards faced enormous challenges. While the US Navy had an immediate demand for a massive number of warships, the shipyards faced difficulties with finding the materials and skilled workers that were needed to fulfill the wartime need.
The William Cramp & Sons shipyard is an example as to the difficulties in converting a civilian shipyard to warship production; it had abysmal keel laid-to-commission durations. Their submarine build times were similarly bad.
Analyzing US WW2 cruiser production was a good training exercise for the methods that Gil Raviv shows in Chapter 10 of his PQ book. I have to say that I have learned a lot.
What can we learn about WW2 from the data? This post did not look at the fates of these warships after VJ day, but I could not escape seeing that so many ships were scrapped shortly after the war ended. The US left WW2 with the largest navy in the world, but it was a navy perfectly designed to defeat the Imperial Japanese Navy – an opponent that no longer existed.
The war created technological changes that affected every aspect of the US Navy:
- Aircraft carriers needed to be redesigned to support jet aircraft.
- US diesel-electric submarines were rendered obsolete first by the German Type XXI boats and shortly after that by nuclear boats.
- Battleships were rendered obsolete by their big guns being outranged by aircraft launched from aircraft carriers.
- Big gun cruisers were rendered obsolete as carriers and their air wings became the dominant ship killers in surface battles. Gun battles between big gun warships became a feature of an earlier time. Cruisers needed to focus more on air defense for the aircraft carriers.
- The US and Canada manufactured ~300K propeller-driven aircraft during WW2. Nearly all were obsolete at the end of the war.
- Jet aircraft rendered anti-aircraft artillery ineffective – the focus would shift to missile-armed vessels.
Whole new classes of warships would be needed going forward to face the threats in the Cold War.