In United States history, early in the Revolution, Colonial marines were used to conduct amphibious landings and raids such as the Battle of Nassau,[2] and the Penobscot Expedition.

Though this history produced a system of landing procedures, the advent of the motor vehicle (the tank in particular) and the airplane required planners to think more critically about the feasibility of amphibious operations.

Ships fitted as troop transports were not priorities for the Navy in fact or in theory, so as a stop-gap measure the responsibility fell to battleships and cruisers to lift Marine landing forces.

In December 1934, a conference between Brigadier General C. H. Lyman of the Fleet Marine Force and Admiral C. S. Freeman was held aboard the flagship Trenton at St. Petersburg.

The Caribbean fleet tested a range of weapons while the Marines moving from ship-to-shore employed machine guns, 81-mm mortars, and the 75-mm pack howitzers against beach targets.

[10] However, many supporting fire practices, both by aircraft and warships, were strictly limited due to safety precautions for the Marines conducting maneuvers along the beach.

[11] The Fleet Landing Exercise Number 2 was conducted from January 4 to February 24 in 1936 marking the beginning of the Culebra/Vieques Inner Range or the Culebra/Vieques Complex as it would be known until 1975 and the closing of the Culebra subranges.

In several testing of various boats, they found that they proved to highly unstable for gun platforms, dangerous in disembarking the troops and were incapable in crossing submerged coral reefs.

While the artificial naval gunfire tests were being continued, the rapid area fire had made the aerial spotting difficult for the pilots.

[5] The Marine brigade gained tactical experience in the amphibious maneuvers ashore but the FLEX 2 had not made any significant breakthroughs in fixing the problems encountered during FLEX1.

[5] The only significant improvements for the landing forces were the new Army Radios that were highly effective for communications and the Marine pack howitzer batteries showing that they could deploy on the shore efficiently.

The pilots however argued that they lacked the special-type of attack aircraft and the proper air-ground communications before they were to gain precision in strafing and bombing.

The origins of the destroyer-transports, or APDs were not widely known at that time until it was first mentioned in an after action report when Brigadier General James J. Meade suggested destroyers might solve the dual problem of a shortage of amphibious transports and naval gunfire support.

While firing a scheduled secondary battery practice on board the USS Wyoming on the last day of the exercises at San Clemente Island, an explosion occurred in the #13 5-inch gun mount, killing one officer and six enlisted personnel.

During these exercises, three Army National Guard regiments participated by "defending" ashore while the Marines of the 1st Brigade attempted a "mock" assault against them.

[8][13] The Army's contribution climbed to three infantry regiments with supporting arms and brigade alternated in the part of landing force and shoreline defender.

The exercise missions were a mixed success at Vieques and Puerto Rico when two patrols were captured, but it was realized that with experience and refinement the concept held promise.

The Vieques Phase, three patrols of one Army and two Marines with four men each were assigned by Rear Admiral A. W. Johnson, Commander of the Attack Force, in reaching the beach under the cover of darkness by inflatable rafts.

[15][16] Four Marines from the Headquarters Company of the 1st Brigade marked the first amphibious reconnaissance patrol launching from a submarine by raft in United States history.

After sunset in the darkness, the submerged submarines navigated to 2 nautical miles (4 km) within the shoreline, following channels until it was able to reach within 1,200 yards (1,100 m) from the beach of Ponce Playa.

[18] This made it easy to discharge the patrols successfully to reach the beachhead without detection from the "enemy" zone of the Army National Guard.

The inserted reconnaissance patrols would deflate their experimental rubber boats upon reaching the shore and re-inflate to rendezvous with the awaiting submarine at a predestined point.

Most of the landing boats were incapable in hauling amphibious tractors, artillery and other important supplies necessary for properly establishing an advanced base.

A drawback to the design was that equipment had to be unloaded, and men disembarked, over the bow or sides, thus exposing them more to enemy fire in combat situations.

During FLEX 6, his plan called for the USS Manley (DD-74) to land Company A, 1st Battalion, 5th Marines via rubber boats during the night, at H-minus three hours, at a point away from the primary assault beach.

[22] This force would advance inland, seize key terrain dominating the proposed beachhead, and thus protect the main landing from counter-attack.