Wikipedia: The Madsen was a light machine gun that Julius A. Rasmussen and Theodor Schoubue designed and proposed for adoption by Captain Vilhelm Herman Oluf Madsen, the Danish Minister of War, and that the Danish Army adopted in 1902. It was the world's first true light machine gun produced in quantity. Consequently, Madsen was able to sell it in 12 different calibres to over 34 different countries worldwide, where it saw extensive combat for over 100 years.[3][4] The Madsen was produced by Compagnie Madsen A/S (later operating as Dansk Rekyl Riffel Syndikat A/S and then Dansk Industri Syndikat A/S).
Up to and including World War I

The Madsen was considered expensive to produce, but was known for its reliability. Thirty-four countries bought the gun, in a dozen different calibres,[5] before and after World War I.
The Imperial Russian Army bought 1,250 Madsens for the cavalry and deployed them during the Russo-Japanese War. The Imperial Russian Air Service used Madsens to equip their Morane-Saulnier G and Morane-Saulnier L monoplanes, mounting the gun to fire over the propeller.[6] The German Army deployed the Madsen in 7.92 mm calibre in 1914, arming infantry companies, mountain troops and later storm troopers.
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Summary of other online comments -
The British Army early on used the Madsen as a Squad Automatic Weapon and found that it was suitable for defense, but too heavy and required too many crew members to make it a successful in attack.