North Korea’s successful rocket launch is likely to strengthen the hand of political conservatives, nationalists and military hardliners at a crucial juncture in the affairs of South Korea and Japan, the two neighbours whose security is most seriously affected.

South Koreans have the most to fear from the North’s militarism. Memories of the unprovoked 2010 shelling of a South Korean island, and the sinking of a navy warship with the loss of 46 lives, are still fresh. With the two countries still technically in a state of war, the threat posed by the unpredictable panjandrums of Pyongyang now looms larger than ever ahead of next week’s presidential election in South Korea.

Park Geun-hye, the conservative leader who is favourite to become South Korea’s first female president in the December 19 poll, has personal reasons for distrusting the North. Her mother was killed in one of several assassination attempts targeting her father, the former South Korean dictator Park Chung-hee, that were ordered by North Korea.

Both Park and her principal rival, Moon Jae-in, say they want resumed talks with Pyongyang. But Park’s demands that the North halt missile tests and cancel its nuclear programme which includes several atom bombs, the building of a light water reactor and expanded uranium enrichment have elicited an angry response, with North Korean state media labelling her a fascist.

In contrast, Moon has said that, if elected, he would resume bilateral aid cut off by South Korea’s outgoing leader, President Lee Myung-bak, and offer new talks without preconditions. Moon’s candidacy is thus more likely to appeal to Pyongyang.

Japan also goes to the polls this weekend in a vote that may produce the country’s seventh prime minister in seven years. Although most Japanese are focused on an underperforming economy that slipped back into recession in the second and third quarters, heightened tensions with North Korea will not help restore the business and consumer confidence that is so sorely lacking.

The election’s outcome remains uncertain, but the Democratic party’s unpopular prime minister, Yoshihiko Noda, is struggling to hang on to office. The man most likely to succeed him is Shinzo Abe, a former premier who is leading a comeback by the once dominant Liberal Democrats.

Abe is a noted hawk and nationalist whose latest visit to Tokyo’s Yasukuni shrine to the spirits of Japan’s war dead in October provoked protests in South Korea and China. He has taken a tough line during the recent maritime disputes with China, and has been active in the past in the cases of Japanese nationals kidnapped by North Korea.

If elected, Abe is expected to resume his previous attempts to ease the constraints on Japanese military action imposed by the post-war pacifist constitution. As proposed, Tokyo would drop a self-imposed ban on exercising its right to collective self-defence, or aiding an ally under attack. This would allow Japan’s military to shoot down a North Korean missile heading for US or other cities, assist a US vessel under attack and facilitate joint operations with US forces.