Leonardo da Vinci presented his military-engineering proposals to Ludovico Sforza in a famous 1482 letter.
Leonardo wrote to Sforza, the powerful ruler of Milan, while seeking employment at the Milanese court. The letter emphasized his abilities in bridges, fortifications, artillery, and military machines. Only near the end did Leonardo mention his competence in painting and sculpture.
The letter is significant because it shows Leonardo presenting himself as an engineer and problem-solver, not only as an artist. Sforza subsequently employed him, and Leonardo spent much of the following decades working in Milan on artistic, architectural, scientific, and engineering projects.
The letter did not mean that every proposal became a working invention. Renaissance patrons often valued ambitious designs and technical expertise, while many surviving Leonardo machines remained sketches or experimental concepts. The document nevertheless explains how his inventions entered courtly and military culture.