The Budget Control Act of 2011, also known as the "sequester," is supposed to cap government spending at set levels. But Congress has repeatedly found ways around that, and one main source of the over-limit spending has been the Overseas Contingency Operations fund.
The OCO fund is for wars, but it's also being used so Congress can pass new spending without running afoul of the sequester, since the OCO fund is exempt from the Budget Control Act.
That doesn't mean the budget deficit hasn't come under control, though. Since 2011, when the Tea Party was at its peak of power and the economy was in the dumps, increased tax revenue from an improving economy has helped push the budget deficit from roughly $1 trillion to $500 billion.