The power of the federal government expanded in several ways and directions during World War I. It intruded massively into transportation, bending the railroads to the public need.
Of course, as far as the war itself, using a draft is a marked expansion of governmental powers. It is a direct exercise of control over individual lives.
The nature and extent of taxes collected rose sharply. (More taxes were collected, the rate of taxation changed, etc.)
New government departments were created, such as the Federal Trade Commission. This increased control over commerce in general.
Governments at war employ centralization as one of their tactics to ensure they destroy internal opposition which would highly impact their external activities. The aim of this form of power centralization is to ensure important military resources are accessible without opposition. This will see an increase in military budgets with a higher level of secrecy in allocations. The tendency to centralize governments during war periods has historically led to "state of emergency" announcements followed by the stripping away of civil rights. The government in this case has too much power that cannot be checked by established institutions charged with that particular responsibility. For instance, immediately after Hitler came to power he began a process of making Germany a single party State. He increased the number of enforcement agents such as establishing the auxiliary police unit (SA). The point was he was going to war and needed to acquire enough power to meet his objectives.
Centralization is one of the methods used to increase a government’s power during a war period. The others include increased military and internal enforcement spending and propaganda to shape the message reaching the masses.
Different governments have different policies about what happens during a war. Such as the Romans who would appoint a dictator type person in the midst of an emergency / war. There are also the governments who might claim to be doing what is right for the country buy taking away peoples children, husbands, wives or supplies.
Hope that helps some.
I assume you are referring to World War I.
There are several ways in which the Government's powers increased during the war:
- Creation of new jobs and agencies: half a million to a million new jobs were created in five thousand newly constituted federal agencies, thus enhancing the bureaucracy and providing more control to the government.
- Pro-war and Anti-Germany propaganda: four-minute-men were created to support and publicize the government's anti-Germany agenda, thus controlling the flow of information.
- Military Drafting: through Selective Services Act, Draftee system was adopted to increase the size of the armed forces, thus curtailing the liberty of citizens.
- Civil Liberties control: using the Sedition Act and the Espionage Act, citizens were prohibited from questioning the government's policies and war efforts. This practically took away the freedom of speech.
- Controlling the economy and manufacturing: to support the war efforts, the economy was controlled in order to manufacture weapon and produce more food and other supplies for the war, thereby enabling government control over production and economy.