To seize steel mills means to take control or ownership of these factories without their consent or through legal means. In this context, it refers to President Truman's decision to nationalize major steel manufacturing facilities during the Korean War.
Related terms
Nationalization: The process by which private assets or industries are taken over or brought under state control.
Command Economy: An economic system where production, distribution, and prices are determined by a central authority (usually government), rather than market forces.
Due Process: The legal principle that ensures fair treatment under law, including notice of charges and an opportunity for a fair hearing before governmental deprivation of life, liberty, or property.