The Amazonian Navy had had Fast Attack Craft (FAC) that were used as harbour defence forces. An experimental craft plus ten production units made up T1-T11. With war threatening again, and knowing how the Argentinians might want another go at humbling the Sisterhood, another class of FAC for harbour defence were designed. These were almost twice the size of the previous WW1 design.
The first order for six was made in 1938. That was to be two each for the major ports. Their major claim to fame was a new high revving diesel for small craft that would replace the more explosive petrol engines in the small boats of the fleet. Completed in June-July 1939, they arrived at their ports straight into a shooting war. Nothing much happened to the first six, they carried out their harbour defence duties, through till July 1940, when the fall of France opened up the English Channel and North Sea as happy hunting grounds for light craft. A request from the UK for small craft that could be used to escort the coastal convoys around the UK led to the Amazonian Navy sending three of the T12's and other escorts. This prompted a new order for a further twelve of this type. Reports from Europe as to their suitability for escort work and attack missions along the Occupied coastline waters also brought another order for six more. More orders were placed through 1942-43, these were to the batch Two configuration with the Bofors 40mm replacing the older slower firing 2 pounder guns. The aft end of the ships was used for various bits of armament from depth charges, mines, and/or an extra 20mm cannon could be fitted there. One of the reason they were well liked was that they did not tend to blow up as easily as the petrol engined MTB's and MGB's of the Commonwealth countries.
The best part of the war for this type was when two of them were used as part of an attack group against the German battleships and cruiser making the Channel Dash in 1942. While the ships managed to get into range of their torpedoes and fire them, no hits were scored on the big ships, though one hit on one of the escorting destroyers was claimed for the group.
Another area of action for this type was for six (one squadron) that were sent to the Solomon Islands to support the various operations by Amazonian forces in the area. Two were lost in night actions against Japanese forces.
Others went to the Mediterranean and fought there. Many were damaged and of the 48 built, 11 were lost to enemy actions. Air attack and being mined were the most popular causes while others were torpedoed or lost to gunfire against other enemy ships. The most unusual was in the Mediterranean when one of them was sunk by Tiger tanks proceeding along the coast road of the north African coast. Those 88mm guns shot it to bits before it could escape out of range. Just an hour later the ANS Melanippe had revenge for the T21 coming across the same Tiger tank group and decimated them before they could escape into he desert.
