1930 London Naval Treaty: An Introduction Part 1 of 5/Articles 1-7

An introduction to a five-part reading of the 1930 London Naval Treaty and the political stories behind its articles.

Article 1 halted new capital-ship replacement construction through 1936 while preserving an exception for ships accidentally lost or destroyed.

Article 2's disposal list let Britain shed ageing, labour-intensive battleships while an overstretched economy faced overdue infrastructure investment.

Britain could concede old battleships while bargaining for the numerous cruisers needed to defend trade, hunt surface raiders, and support a concentrated battle fleet.

A failed 1927 negotiation and unequal cruiser and destroyer fleets help explain why the 1930 agreement involved more than battleship numbers.

Articles 3 and 4 define a carrier by its exclusive aircraft role and prevent sub-10,000-ton carriers from mounting guns above 6.1 inches.

The London negotiations reduced the influence of professional naval officers after political leaders blamed naval delegations for the earlier Geneva failure.

Japan's sub-10,000-ton Ryujo demonstrated how the Washington rules could support fleets of small carriers, prompting London to close the category.

Rapid growth in aircraft size made the apparently economical small carrier a difficult long-term naval aviation platform.

Article 5 aligns carrier armament rules around a 6.1-inch or 155-millimetre limit, showing how measurement standards defined treaty categories.

A discussion of 152- and 155-millimetre weapons connects the treaty's calibre wording to later artillery standards and speculative future naval guns.

Article 6 applies standard displacement rules across surface warships and defines submarine displacement without fuel, oil, fresh water, or ballast water.

Article 7 sets a 2,000-ton and 5.1-inch baseline for submarines while allowing a few larger boats and a special French exception.

Large cruising submarines could use reusable deck guns against merchant traffic, conserving expensive torpedoes for warships.

Interwar boats spent most of a patrol on the surface, so their hulls and endurance should not be judged by the standards of later underwater submarines.