[en] Iron-based superconductors (IBSs), discovered in 2008, formed the second high-T _c superconductor family after cuprate superconductors, and over the past decade have been the subject of extensive research into their physical nature and application potential. With their attractions of very high upper critical fields and small electromagnetic anisotropy, tremendous advances have been made in wire research and development (R and D) to explore the potential of IBSs for high-field applications. In recent years, rapid progress was made on the critical current density (J _c) of the 122-type IBS wires based on a powder-in-tube technique. Encouraging breakthroughs were made, including a high transport J _c exceeding the practical level of 10⁵ A cm⁻² (at 4.2 K, 10 T) and the first 100 meter-class wire. This review covers the state-of-the-art techniques and their mechanism in realizing high transport J _c with respect to the grain connectivity, grain texture and flux pinning for IBS wires and tapes, as well as the temperature and field angle dependence of critical currents. The mechanical properties, AC losses and magneto-thermal stability of IBS wires are investigated, and further improvements in IBS conductors for large-scale applications are proposed. In addition to long wire fabrication, this review also highlights some remarkable advances relevant to practical applications, including scalable process optimization, copper sheaths, multifilamentary fabrication, and superconducting joints. Finally, a summary and outlook for R and D for IBS wires are presented. (topical review)