alone can soften and neutralize all the targets in the island in a matter of weeks.  Taiwan is not far away from China.  Today's China artillery units have long range distance, anti-buners and anti-trench capabilites in addition to high precision capabilities.  It can go very deep into the ground or disperse in the air at the target area depending on the type of warheads. They have all sort of  smart sensors capabilities incorporated into the weapon. Some even has the capability to lay landmines from the air.  It can really mess things up.  Almost everything now is greatly adavanced.

Being a nation surrounding by big powers, China always prepares for conflict.  I am sure China has amassed a enormous amount of firepower ready for conflict for at least forty or fifty years with any nations. 

The problem with Taiwan is an island.  It separates from other country by a large body of waters. Logistically resupplying its firepower is a nightmare.  Any ships cross the waters is visible in the sky like a sore thumb.  It will be neutralized by China's missile defense or drones.  Once they run out of ammo, it is game over.

For the last couple years, The US Department of Defense run thousands of war stimulated scenario with China over Taiwan in a supercomputer.  In all case, US and NATO all got defeated if they don't have some sort of secret weapons from the future.