A quench and temper steel alloy is disclosed having the following composition in weight percent. C0.1-0.4 Mn0.1-1.0 Si0.1-1.2 Cr9.0-12.5 Ni3.0-4.3 Mo  1-2 Cu0.1-1.0 Co  1-4 W 0.2 max. V0.1-0.6 Ti 0.1 max. Nbup to 0.01 Taup to 0.01 Al  0-0.25 N0.1-0.35 Ce0.006 max. La0.006 max. The balance of the alloy is iron and the usual impurities found in similar grades of quench and temper steels intended for similar use or service, including not more than about 0.01% phosphorus and not more than about 0.010% sulfur. A quenched and tempered steel article made from this alloy is also disclosed. Further disclosed is a method of making the alloy.