Taiwan's defense problems are far greater than they were when the Taiwan Strait was an insurmountable barrier to Chinese invasion. But Taiwan still needs to defeat the Chinese in battle to retain their independence. There is no cheap asymmetrical way to defeat China. Taiwan must raise the costs of invasion at every part of the combat spectrum, from invasion to resistance, to deter China.
This is a nice summary of issues today for the defense of Taiwan.
While it is true that Taiwan cannot match China in the air or at sea, I don't think it is wise for Taiwan to abandon those areas to the Chinese.
Air power--if it is made survivable--can at least complicate and thwart early Chinese airborne operations that might seek a bolt-from-the-blue invasion. Just surviving makes the Chinese worry about what Taiwan can do in the air. Bolstered by Taiwanese missiles (ballistic and cruise) that could take the offensive roles for operations against Chinese bases on the mainland, the aircraft could focus on air defense over Taiwan and the eastern approaches to the island, and limited critical strike missions against Chinese forces ashore on Taiwan.
Sea power cannot be used to control the Strait of Taiwan. The balance of air and naval power is too out of whack for that. We have to be cautious approaching as close to China as Taiwan starts out. So in the strait, Taiwan needs sea denial weapons like shore-based missiles, submarines, and small attack craft that can hug the western coast of Taiwan to hide from radar.
But Taiwan still needs basic sea control ships for the east to hold open their sea lines of communication. What good does it do Taiwan to create a successful "hedgehog" defense of Taiwan that absolutely deters Chinese invasion only to make it easy for China to simply blockade Taiwan and starve them into submission?
So yes, in some ways Taiwan needs asymmetrical methods to counter China's air power and sea power in the Taiwan Strait. But Taiwan needs force-on-force at sea off the east coast and in the air over Taiwan even if everyone knows that eventually the Taiwanese will lose control of the air through attrition alone. But Taiwan needs whatever time their air force can buy to deny China control of the air over Taiwan. We've shown what air supremacy means for enemy armies, haven't we?
And Taiwan absolutely needs force-on-force ground capabilities. Just because China is far bigger is no reason for despair. How much bigger was Russia than Finland in 1939?
Finland did not have a 100-mile wide anti-tank ditch. But they did have well trained and motivated troops who took advantage of their terrain to hold off the Russians for three months and inflict heavy casualties on the Russians.
Taiwan has the advantage of facing invaders who cannot retreat into the depths of Russia to regroup as the Russians could, and then keep coming. If Chinese invaders are forced back at their bridgeheads and airheads, they must surrender.
So Taiwan needs an army that is mobile with good command and control so that Taiwanese units can quickly react to Chinese invasion sites and quickly throw the Chinese back before the initial lighter forces can gain heavy weapons reinforcements and depth by marching out from invasion sites or drop zones.
And these ground units need ample air defense weapons to take up the slack as their air force is defeated.
While Taiwan is moving toward a volunteer army that is smaller but better, don't forget quantity. Taiwan will need lots of reservists who can at least conduct point defense of cities, towns, airports, ports, tranpsortation chokepoints, and military facilities, freeing the army brigades for conventional combat. Such forces will also be a latent threat for resistance in areas that the Chinese manage to seize or in the worst case if China conquers Taiwan.
If Taiwan's missile and air power can savage China's amphibious and air transport elements, the Chinese will have problems coming back for more even if they want to try.
And not only is it crucial for the Taiwanese to very rapidly counter-attack Chinese forces that make it to the island, it is very important for the Taiwanese to completely throw the Chinese off the island before a ceasefire. If China holds any territory on Taiwan at the end of hostilities, it will becomes a massive PLA army base that will finish the conquest of Taiwan in round 2.
Finally, just the possibility that Taiwan could fight for 3 months should give China pause. After 3 months, Western powers were moving to intervene on the side of the Finns despite the ongoing war against Nazi Germany. With three months to ponder the pending destruction of a democratic country by a belligent China, surely America would intervene as would Japan and maybe South Korea, Vietnam, Singapore, and Australia who might conclude that they'd rather have a China held at the Taiwan line than closer to them with their appetite for more territory whetted by Taiwan.
Taiwan cannot abandon efforts to defeat Chinese forces in battle. The Taiwan Strait is no longer the ultimate trump card in preventing a Chinese invasion, but it still is one heck of an obstacle that small states around the world would love to have as they ponder larger, hostile neighbors.
Imagine the cost of trying to build such an obstacle if Taiwan was 100 miles further west. Isn't building a military capable of fighting for three months--which might be enough to defeat an invasion--a bargain by comparison?
And heck, if that seems too much, Taiwan might have to go nuclear. If China sees little need to help us halt North Korean and Iranian efforts, why whould we interfere with Taiwan's clear need to deter China form invading?
UPDATE: Thanks to Mad Minerva for the link.
UPDATE: Thanks to The View from Taiwan for the link.