China’s efforts to ‘modernize’ its arsenal? Are you kidding me? China had, until a few years ago, a tiny, neglected nuclear arsenal smaller than France’s mounted mostly on 1980s-era storable liquid rocket boosters — the equivalent of US Titan missiles (those are still the mainstay of the ICBM force, according to Wikipedia). That arsenal seriously needed modernization — for safety/infrastructure-maintaining reasons if nothing else.
Now, even with its recent modernization, China has a nuclear arsenal SMALLER THAN FRANCE OR THE UNITED KINGDOM (it has more megatonnage, but megatonnage is meaningless in a world of 550-kt low-yield, low-weight MIRVs). Whatever you say about proportional defense spending, such an arsenal is not adequate for a reasonably powerful (maybe in 10–20 years…) nation of 1.4 billion people.
China’s military expansion is not abnormal. The economy is growing, and China is deeply enmeshed in the global economy. All nations require military forces to defend their interests worldwide, and China is no different.