The reason why China made provocation in Senkaku is now clear. It is one of their militaristic expansionist policies. They want to push ahead exploration of gas fields that are on Japan-China border on East China Sea.
Its existence was known since the late 1960’s. Japan did not go on exploring the field unilaterally, because we (Japan) know international agreement. According to the agreement, if the oil and gas are located across the border, relative countries should have right to the resources according to the ratio by which the country’s territory owns. Since 2005, when it was discovered that China was secretly making surveillance of the fields within and out (therefore within our territory) their territory and working to build drilling equipment, this matter has been a disputed between Japan and China.
Most of the gas is in Japan territory. They don’t care. What they want, they get it. With force, if necessary. With intimidation, if necessary. It was all planned by the Chinese government from the start.
They let innocent looking fishing boat intrude into our territory (Senkaku Island located south of the gas fields). Let them crush into our coast guard ship. Let us capture their men. Japanese TV stations film footage of that situation and broadcast it on TV. Chinese media records that broadcasting and let Chinese people see that on TV, over and over and over again. Let them uproar and create crisis, setting up some road protest marches (only to the extent government can make sure they don’t turn themselves into anti-government protest). By then the crisis has been elevated into diplomatic warfare. Chinese officially smear Japan (not China - surprisingly or naturally depending on perspective) as invader.
“How dare you, Japan”. “You were invader before and you are now”.
Now what? They got strong domestic backing to go ahead with the exploration of the gas fields.
“Japan is once again an invader. They capture our southern island of Senkaku (they call it Diaoyu). They are trying to take our natural resources. This is an act of self-defense against invasion of our country by Japan”.
This is an act of war by China against Japan. Should we go to real battle? Can we? Do we have strength and guts? How about America? I don’t know. China got the vote. As always the case of the war, aggressor got the vote.