In terms of gains from trade, why is it true that taxes cause deadweight losses?

Gains from Trade

Gains from trade refer to the increase in consumer and producer surplus that occurs when countries specialize in the production of goods and services in which they have a comparative advantage and then trade with others.

Deadweight Losses

Losses in social welfare, usually measured in terms of lost revenue or surplus, resulting from inefficiencies in a market or the economy.

Taxes

Necessary financial levies or assorted kinds of dues imposed on an individual by a governmental structure to facilitate government finance and numerous public investments.