It does look like SoftBank and Sprint are making a coherent case for the technical and market synergies of their merger. Nevertheless it is really quite a bold move for a Japanese mobile operator.
NTT DoCoMo has made a number of strategic investments in Asia (e.g. TATA Teleservices in India) in recent years but it got its fingers burnt in the cellular and dotcom boom. NTT DoCoMo tried to enter the international mobile operator licensing/purchasing/investment market too late. In 2001, NTT DoCoMo invested around US$ 10.2 billion in then known, AT&T Wireless Services Inc, in an attempt to encourage adoption of its then more advanced wireless services (remember iMode handsets being introduced into the US market?). NTT DoCoMo was having considerable success with its iMode services in the Japanese market and NTT DoCoMo tried to spur the adoption of its iMode mobile data technology in a number of international markets through investment and/or joint venture marketing and supply of handsets.
iMode failed to capture the imagination of the US consumer. The technology only had limited success and NTT DoCoMo had to discretely withdraw from a number of markets. SoftBank may have more success than NTT DoCoMo, as it is not evangelizing a ‘walled garden’ business model and technology.