That is a sober warning for the future. The OP analysis is dead-on and it was well-known that an income-taxed population could collateralize a coming WWI, which is why top rate rose from 1% to 90% in that same decade.

And, u/Inquimous, payroll tax is and has been ruled as a class of income tax, so it needs to be considered all one. And indeed, other excises and tariffs have not lost their indirect force upon the populace one whit.

I'm not confident of the accuracy of the inflation adjustment of this axis, but the base data is good.