Chinese claim to restore borders around 1750 qing dynasty rule. 1911 was when british had already taken majority of hong kong, india , pakistan regions.
1911 is world war 1 date chinese claim of modern day china by, governments in China Communist party of china and in taiwan Nationalist governemnt both claim 1750's qing dynasty china territory to be modern day chinese state based upon.
Hence the disputes. Chinese consider british as opressors and foreigners similar to japanese.
Listen to chinese national anthem. 起来 起来! Well now they have 起来了 and the british and Japanese and enemies of chinese will pay for down fall of china for 300 years.. Only 300 years when china was not a super power of world histroy of 5000 years.. Only 300 years china was opressed by british and Japanese and even russians.
Now its their golden age watch them take all the glory back.
They see india and pakistan as left over legacy of british just like hong kong taiwan and macau.
Only difference is pakistan mend its problems with them and became strategic partner and signed treaty of friendly neighbours alomg with russia.
India needs to do the same asap and give up chinese land in order to be friends with china. Then they can together take care of usa and europe.
But if india is in opposite camp .... They are enemies.
2019 till 2045 is not a good time to be enemies with china.
You can clearly see ladakh and leh being part of china in this map. Alomg with some afghan, pakistan and tajik land.