[citation needed] The British Chiefs of Staff Committee concluded in May that if France collapsed, "we do not think we could continue the war with any chance of success" without "full economic and financial support" from the United States.

[3] The US government was sympathetic to Britain's plight, but US public opinion overwhelmingly supported isolationism to avoid involvement in "another European war".

Reflecting that sentiment, the US Congress had passed the Neutrality Acts three years earlier, which banned the shipment or sale of arms from the US to any combatant nation.

[5] The Prime Minister Winston Churchill initially rejected the offer on 27 May unless Britain received something immediate in return.

On 1 June, as the defeat of France loomed, Roosevelt bypassed the Neutrality Act by declaring as "surplus" many millions of rounds of US ammunition and obsolescent small arms and authorising their shipment to Britain.

By August, while Britain was reaching a low point, US Ambassador Joseph P. Kennedy reported from London that a British surrender was "inevitable".

[6] On 2 September 1940, as the Battle of Britain intensified, Secretary of State Cordell Hull signaled agreement to the transfer of the warships to the Royal Navy.

The US accepted the "generous action... to enhance the national security of the United States" and immediately transferred in return 50 Caldwell, Wickes, and Clemson-class U.S. Navy destroyers, "generally referred to as the twelve hundred-ton type" (also known as "flush-deckers", or "four-pipers" after their four funnels).

The destroyers were in reserve from the massive US shipbuilding program during World War I, and many of the vessels required extensive overhaul because they had not been preserved properly while inactivated.

[3] Churchill also disliked the deal, but his advisers persuaded him merely to tell Roosevelt, We have so far only been able to bring a few of your fifty destroyers into action on account of the many defects which they naturally develop when exposed to Atlantic weather after having been laid up so long.

The United States Coast Guard vessels were ten years younger than the destroyers and had greater range, which made them more useful as anti-submarine convoy escorts.