Leonard Brooks was born in London, England, in 1911. In 1912 his family immigrated to Canada and settled in North Bay, Ontario. For a short time he studied at Ontario College of Art in Toronto and taught at the Central Technical School. He spent a year in Europe, and joined the Royal Canadian Naval Volunteer Reserve in May 1943.

During the Second World War he worked as a Petty Officer and designed war posters for the Naval Art Services. In 1944 he was made an Official War Artist.

He went on every ship he could, including corvettes, aircraft carriers and submarines. He painted the movements of naval ships off the coast of Scotland, and the activities of mine sweepers and motor torpedo boats in the English Channel for both the British and Canadian navies.

Leonard also recorded the daily activities of the sailors at war. At night he would go up on deck and sketch the patrollers. Life on board the ship was not always about fighting. He felt that daily activities helped to win the war, and that "There was never a dull moment, when they weren't on watch, or peeling potatoes, or doing something - They could be sunk in one moment, or blown up, or hit a mine."

Sketching on ships during rough weather was difficult, as Brooks explained in a letter to the National Gallery: "Forgive the scrawl. We are rolling along in great style and the wardroom table gives a kick every so often. I have managed to work a system of scribbling and taking notes on this kind of rough day. By devious ways I scribble a note or two on rough paper—dodge the spray and find my way below to redraw and fill in as much information as I can—dash up again and repeat the performance. It looks rather ridiculous but is very effective."

For Brooks war art was special in that it "doesn’t add up to great art, but these paintings, have left a legacy of truthful seeing and feeling, and caught for posterity some of the deep and terrible days of courageous despair and brave hopes for a better future".

After the war, Brooks remained a full time painter and obtained a grant from the Department of Veterans Affairs to study art in Mexico. He taught for several years in San Miguel de Allende, north of Mexico City.

Brooks has published a number of works on watercolour and oil painting techniques, and his skill as an artist has gained him worldwide recognition. Leonard Brooks passed away on November 20th, 2011 at the age of 100.