What could happen if North Korea attacked South Korea?

Fears of conventional or chemical attack are more likely

(CNN) – North Korean Special Forces attack a mock-up of South Korea’s presidential compound.

Propaganda footage of what Pyongyang claims it could do to Seoul if provoked.

As Washington insists all options are on the table, South Korean officials warn the military option is unpalatable.

One man involved in calculating the casualty impact says they’re working from at least a dozen different scenarios, including nuclear attack.

Kim Tae-woo of Konyang University said, “If North Korea uses the Hiroshima bomb size nuke attack against Seoul city then within the one month over 500,000 people will die and after that more people continue to die because of the side effects.”

As Kim Jong-un watches special commandos train, one of his top diplomats warns nuclear war could break out at any moment. A well-used threat that few in South Korea believe would actually happen.

Fears of conventional or chemical attack are more likely.  South Korea’s defense ministry believes Pyongyang has up to 5,000 tons of chemical weapons in stock.

Park Hwee Rak, of Kookmin University said, “I don’t think the US is fully prepared to cope with all the side effects of the pre-emptive strike”.

However, opinion is split in South Korea, some are optimistic Kim Jong-un may not even react to an American pre-emptive strike.

Chun Yung-woo of the Korean Peninsula Future Forum said, “I see less than 1% chance that North Korea responds if he responds with artillery and bombardment then he knows within a matter of days or weeks the North Korean regime will no longer exist.”

A 2004 study by the Joint Chiefs of Staff estimated that some 2.3 million people could be killed or injured in Seoul and in its surrounding areas within the first 24 hours.

These are details from a confidential report leaked by a deputy parliamentary speaker. He says he wants to make sure the U.S. fully understands the consequences of any military action.