The Diet session that closed last Friday set a significant precedent for Japan's evolving security policy debates, paving the way for the first "wartime" deployment overseas of the Self-Defense Forces. That was the most important feature of the extraordinary session. What prompted the SDF move was, of course, the U.S. military campaign against terrorism following the Sept. 11 atrocity.

The swift passage of an antiterrorism bill, designed to provide logistic support for U.S. forces, reflected not only the urgency of international efforts to combat terrorism but also Japan's commitment to play a visible role in the U.S.-led campaign. No doubt the Diet, not just the government, was still smarting from the nation's failure to provide physical support in the 1991 Persian Gulf War. That is also why a measure to update the 1992 law on U.N. peacekeeping operations -- designed to ease the curbs on the use of weapons -- also sailed through the legislature without difficulty.

Times have certainly changed. Previously, security issues used to touch off raucous debates in the Diet, often leading to violence. Voting in plenary sessions took days, not hours, as the opposition parties resorted to all manner of delaying tactics. In the last Diet, nothing of the sort happened, despite the fact that the antiterror bill called for wider SDF activities than ever before. The official line was, and still is, that Japan is constitutionally prohibited from taking joint military action.

The Democratic Party of Japan, the largest opposition group, initially expressed basic support for the antiterror bill -- something that would have been unthinkable in previous sessions. In the end, though, having failed to reach a last-minute deal with the Liberal Democratic Party on a less important issue, the DPJ went along with other opposition parties. The DPJ episode, however, illustrated that security discussions in Japan, not just in Parliament, were beginning to converge along more realistic lines.

This is a welcome development. Practical debate, not the abstract rhetoric that marked past security arguments, is what the nation needs urgently as it prepares to take a positive role in international peacekeeping operations.

The flip side is that some key questions were left largely unanswered, reflecting in large part the ambiguity of constitutional interpretations: Wouldn't SDF support lead to military involvement if the fighting intensified or expanded? In what geographical areas would SDF troops operate? Nor were these questions resolved during the summary review of the basic deployment plan, which the government submitted for ex post facto approval.

The government emphasized that SDF deployment would not constitute collective self-defense -- which is considered taboo because of constitutional constraints on the use of force -- as long as it was confined to logistic and humanitarian activities. The Diet, of course, must see to it that the military does not cross the lines. But the way in which it examined features of the deployment arrangement, including the dispatch of destroyers to the Indian Ocean, suggests that the Japanese Parliament is not fully equipped to monitor the SDF's expanding operations abroad.

Beyond that, the "antiterror Diet" exposed latent weaknesses in both the ruling and opposition camps. First, the debate on SDF dispatch revealed different outlooks on security among the three parties in power -- the LDP, New Komeito and the New Conservative Party -- although the bill itself was supported by all three. In the process, the tripartite alliance showed itself to be not as united as it claimed to be. The debate also brought to a head the rift between Prime Minister Junichiro Koizumi, not necessarily a staunch advocate of coalition politics, and his procoalition critics.

Second, the DPJ, a collection of splinter groups, failed to vote in unison, with some members dissenting from party decisions. Thus the leading opposition party demonstrated, by default, that it was neither willing nor able to take over the reins of government. The challenge ahead for the party is to put its house in order to make itself a more credible opposition force. That is the only way to stake out a more influential position in the next regular Diet session, which opens in late January.

The consolation is that the exposure of political fault lines, while introducing elements of confusion into the debates on security issues, seemed to have awakened major parties, particularly the LDP and the DPJ, to the pressing need for internal reform. The warning is clear: They must first get their acts together in order to bring more realism and dynamism into security debates.