Lack of food and fodder, buy it!
Short of armor, buy it!
Not enough warhorses, buy it!
Magic scrolls are useful, buy them!
Magic crossbows are powerful, buy them!
Magic crystal cannons are great for city defenses, buy them!
...
All for the sake of winning the war, what is a little expenditure?
The inevitable result of "buy, buy, buy…" is rapid inflation in fiscal expenditure.
If the budget is maxed out, then continue to borrow. Repayment is a problem for the future.
Perhaps by the time they realize the pressure to repay, the Moxi Duchy would have gone down the road of borrowing new to repay the old.
What will determine the final outcome is not everyone's will, but how long this war will last.
If the war is short-lived, with the wealth of the Moxi Duchy, repaying the debt in the future wouldn't be difficult.
But if it stretches on for three to five years, the question isn't about repaying the money, it's about when the debt bubble will burst.