Ever since it surrendered to the allies at the conclusion of WW2 Japan's military effort has been homebound. The Japanese Self Defence Force has been precisely that - remaining vigilant to outside threats but constitutionally restrained from striking the first blow. Now, with an assertive China throwing its weight around in North Asia, there's a developing inclination among Japan's leadership to take its tactical lead from another playbook: that the best form of defence is attack. Many in Japan - young and old - worry that's leading their nation down a path to war.