THE present problem of naval limitation hinges on the ability of the countries involved to arrive at a method of putting various types, ages and sizes of cruisers on a comparative basis -- in common parlance, to evolve a "yardstick" for equitably evaluating their varying qualities. Tonnage is the basis on which ships have previously been compared. The plan now is to take into consideration the other characteristics of the cruisers. These characteristics may be put under the four following heads: Speed. Age. Cruising Radius. Fighting Value.

Let us assume an ideal type of cruiser and assign it the value of 500. This value should be made up of 100 points for perfect speed, 100 points for perfect age, 100 points for perfect cruising radius, 200 points for perfect fighting value. The next step is to determine the condition of each of these qualities.

1. Speed. The ideal cruiser may be assigned the highest probable speed that a cruiser is likely to attain. At present forty knots would appear a reasonable figure to take. The lowest practicable limit of useful speed for any work is approximately fifteen knots. If we say the speed value of a cruiser is zero at fifteen knots, then the range from fifteen to forty knots would represent 100 points on the value of our cruiser. Thus each knot below forty knots would equal 4 points of speed value, and a thirty-knot cruiser would have a value of 60, a twenty-five-knot cruiser a speed value of 40, etc.

2. Age. The practice established by the Washington Naval Reduction Conference and Treaty, which crystallized the opinions of the various Navy Departments, has been to fix the useful life of a warship at twenty years, considering it obsolete thereafter. Adopting this principle, we value a new cruiser at 100 and take off 5 points for each year after the cruiser is commissioned. Thus a cruiser eight years old has an age value of 60 points in the total.

3. Cruising Radius. We take cruising radius to mean the longest radius at the most economical speed. As recent design has raised this radius up to approximately 15,000 miles, we shall assume that the perfect cruiser has a cruising radius of 15,000 miles and that the cruising value of any cruiser varies from 100 as the cruising radius varies from 15,000. If less than 15,000 miles, it will have a value less than 100, if more it will have a point value of more than 100.

4. Fighting Value. This item does not take into consideration all of the fighting qualities because, of course, the conditions already noted influence fighting value. The fighting value here considered is the striking energy of the ship's main battery and her defensive strength as represented by her armor plates. The striking energy of the ship's battery varies with the range, size and the calibre of her guns, and the resistance to gunfire varies with the range and the thickness of her armor. Thus the fighting value of a ship should be established at the range at which the ship has just sufficient armor to protect it against a shell of the calibre which she is capable of firing. To illustrate -- a ship mounts five 6" guns and is protected by 3" armor over her vitals. The armor will resist penetration of 6" shells at 15,000 yards. Then 15,000 yards is the range at which we shall figure the fighting value. We compute the resolved normal energy of five 6" guns at 15,000 yards. We find the ideal value or highest striking energy that the present design of cruiser will be likely to give and assume this value for our perfect cruiser. We have allowed 200 points for fighting value in our total value of the perfect cruiser, so we now can figure the percentage of that number to allot the cruiser which is being studied.

The total of the four figures thus obtained is the yardstick value of our cruiser.

Applying this method to several types of cruisers now in existence, we find that the most powerful cruiser built or building will have a striking energy derived under the above conditions of approximately 25,000 to 26,000 foot tons. We can therefore assume a perfect fighting value of 30,000 foot tons for our perfect cruiser. A few examples will make the system clearer:

A modern cruiser of the PENSACOLA class having ten 8" guns (the heaviest battery installed in any modern cruiser) gives the following results:

Commissioned 1929 -- Age value 100
Speed 33 knots -- Speed value  72
Cruising radius 13,000 miles -- Cruising value  86.66
Ten 8" guns -- Fighting value 166.66
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    Total 425.32

A cruiser of the DETROIT class, built and commissioned in 1923, gives the following results:

Commissioned 1923 -- Age value  70
Speed 34.8 knots -- Speed value  69.72
Cruising radius, 10,000 miles -- Cruising value  75
Twelve 6" guns, 3" armor -- Fighting value  57
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    Total 271.72

Old cruisers of the CHARLESTON and ST. LOUIS class give these results:

Commissioned 1904 -- Age value 0
Speed 21.5 knots -- Speed value 26
Cruising radius, 4,000 miles -- Cruising value 26
Twelve 6" guns -- Fighting value 50
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    Total 102

Applying the same procedure to a French cruiser of the SUFFERN class, mounting eight 8" guns but without armor protection (in case there is no armor fitted, the normal striking energy should be computed at the range at which shell has the lowest striking velocity), we get the following results:

Commissioned 1927 -- Age value 90
Speed 34.5 knots -- Speed value 78
Cruising radius 5,000 miles -- Cruising value 33
Eight 8" guns -- Fighting value 106
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    Total 307

With a British cruiser of the LONDON class (eight 8" guns with 3" armor protection) we get the following results:

Commissioned 1929 -- Age value 100
Speed 32 knots -- Speed value  68
Cruising radius 10,400 miles -- Cruising value  69.5
Eight 8" guns -- Fighting value 133
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    Total 370.5

The Geneva Conference of 1927 was stalemated because the fundamental conditions which determine the cruiser needs of the United States and Great Britain are radically different.

Great Britain's cruiser needs are best fulfilled by a multiplicity of units of normal cruising radius, mounting batteries more powerful than could be mounted on auxiliary cruisers converted from the ships of the merchant marine of the other maritime powers. These requirements are due to the great number of sea routes which it is necessary for Great Britain to keep open. Great Britain has numerous strategically located naval bases and a large merchant marine capable of rapid conversion into auxiliary cruisers.

The requirements of the United States are for large cruisers of long cruising radius, capable of mounting heavy batteries more powerful than could be mounted on any converted cruiser; but the United States does not require the multiplicity of units needed by Great Britain. These conditions arise out of the lack of American naval bases located in strategical points throughout the world, and the small number of ships in the country's merchant marine capable of conversion to auxiliary cruisers.

At Geneva it was found that when the tonnage of the type of cruiser based upon the needs of the United States was multiplied by the number of units required by the conditions facing Great Britain, the figure arrived at was so large that the result was not limitation of cruisers but expansion of the total cruiser tonnage. As a result the Geneva Conference failed.

The suggested yardstick would allow each country to arrive at a solution of its cruiser requirements, and yet the total battle effectiveness of the two cruiser navies would remain equal. By building cruisers mounting a smaller number of guns and with a shorter cruising radius, Great Britain would have more cruisers and a greater total cruiser tonnage, as it takes less tonnage per gun to mount ten 8" guns in one ship than it does to mount ten 8" guns in two ships. However, even if Great Britain should have a greater tonnage of cruisers, yet her power would be equaled by the larger American cruisers with larger batteries.

Another factor to be considered is that of cost. Ships are constructed, maintained and operated more cheaply in Great Britain than in the United States. But it would cost relatively more to build, maintain and operate two ships mounting five 8" guns than to build, maintain and operate one ship mounting ten 8" guns. Therefore if Great Britain chose to have a greater multiplicity of units, the cost of equal cruiser fleets, divided into such types as each country found necessary for her needs, would be more nearly equal than if the same amount of tonnage were maintained under the conditions prevailing.

The yardstick for cruiser measurement here proposed seems to offer a solution to the deadlock existing between the United States and Great Britain, allowing the cruiser fleet of each to be based on the requirements of that nation, yet still maintaining parity between the battle strength of the two navies.

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  • H. L. VICKERY, Lieutenant-Commander (CC), United States Navy, Bureau of Construction and Repair
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