Toshiba Machine's 1982–84 sale of CNC milling equipment to the USSR is credited with helping quiet Soviet submarine propellers

Between December 1982 and 1984, Toshiba Machine — with Norway's Kongsberg Vaapenfabrikk supplying the numerical-control systems — sold the Soviet Union's Technical Machinery Import Corporation eight large multi-axis CNC milling machines and the software to run them, in violation of CoCom export controls. The equipment let Soviet yards machine large, precisely contoured submarine propellers, and is popularly credited with letting "the submarine technology of the Soviet Union to progress significantly as it was being used to machine quieter propellers" — degrading the US Navy's acoustic detection advantage.

The frequently repeated claim that the quieter propellers cut US submarine detection range by roughly half is [unverified-quant — needs primary; source is Wikipedia/secondary]: the cited article attributes the 50% figure to Congressman Duncan Hunter, and it has not been traced to a primary Navy or Pentagon damage assessment. The verification is queued at question-verify-toshiba-kongsberg-submarine-detection-quant. The core historical fact of the sale is Tier-4 but uncontested; the load-bearing number is not.

The scandal detonated into a 1987 US–Japan trade crisis — import bans, Congressmen smashing a Toshiba radio-cassette player with sledgehammers on the Capitol grounds (July 1, 1987, per contemporary press: UPI, upi.com/Archives/1987/07/01/Lawmakers-hammer-Toshiba/3984552110400/; the cited Wikipedia article instead places the stunt "in front of the White House") — and in popular memory it is often miscredited as the trigger for the 1988 Exon-Florio Amendment. The legislative record instead points elsewhere: claim-exon-florio-triggered-by-fujitsu-fairchild-not-toshiba. The scandal fell entirely within the Tokyo ambassadorship of claim-mansfield-amendment-sponsor-longest-serving-ambassador-to-japan.