Most countries consider their official language to be an area of state responsibility requiring "planning" by government agencies or special institutions. Language, from this point of view, is seen as a collective good whose development can, and should, be controlled. Typical language-planning activities are aimed at fending off contaminating influences from other languages, protecting the norm against decay, or steering the language in a desired direction.
The Japanese government's deliberate intervention in linguistic development amounted to language planning by the time of the Meiji Era, although the term itself didn't come into currency until the 1950s. Tessa Carroll's book provides an overview of activities and attitudes pertaining to language planning in Japan as well as a state-of-the-art account of the Japanese language and society. Although not much original research is reported, the book covers a wider scope than several other English-language books about language planning in Japan.
To Carroll, language planning is not a field limited to the technicalities of spelling, grammar or pronunciation. Language planning, she argues, is at the heart of the formation of all political entities. Although she reaches back to the Meiji Era and sometimes earlier, her main focus is on the final two decades of the 20th century -- when planning schemes served as a means of "projecting a self-image for Japan for the 21st century" for both internal and external consumption.