As well-intentioned as some defence scientists may be in questioning our purchase of expensive aircraft, they do not fully understand the threats that our little red dot faces ("Open debate needed on defence policy" by Dr Paul Tambyah; last Friday and "Don't underestimate need for strong military" by Mr Adrian Villanueva; last Saturday).

The threats that we face are multi-faceted.

Unless our defence forces are strong, anyone can walk in and destroy all that we have built over the past 50 years.

It is easy to argue for a cut in defence spending. However, once we go down that route, there is no return.

New Zealand is a classic example.

At its peak, the Royal New Zealand Air Force was a force to be reckoned with, and was active in the Pacific theatre during the war.

After the war ended, the air force was reduced as part of a defence spending cut.

It no longer has any capacity to exert its air superiority.

While New Zealand is fortunate to be located at the far end of the earth, Singapore is different.

It would be naive to believe that when Singaporeans are happy, they will naturally step up and quash any hints of terrorism - domestic or otherwise.

As a major financial and trading centre, we are highly vulnerable.

Any hint of trouble will affect our survival and lead to an exodus of foreign talents and companies. That will spell the end of Singapore.

Singapore must remain like a porcupine. The hawks and eagles swarming around will not dare to swoop down on us, knowing the excruciating pain we can inflict on them.

Patrick Tan Siong Kuan