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Invisible Letter:

May 6, 1775

Sir / If you will be so kind as to deliver to / Mr. of Boston, the Papers which I / left in your care, and take his Receipt for the same, / You will much oblige / Your Humble Servant / (erased) / Saturday May 6th 1775


Visible Letter:

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Woburn May 6th 1775 / Sir, In compliance with your desires I embrace this / first opportunity that has offered since I left / Boston to send you some account of the / Situation of affairs in this part of the Country- / I need not trouble you with a particular account / of the affair at Concord on Wednesday the 19th [ ] / nor of the subsequent gathering at Cambridge [ ], as / you have doubtless already / better intelligence of them affairs than I am able to / give you.

The only information that I can give you / that can be of any consequence [page loss] lately received / from a Field officer in the Rebel / Army (if that mass of confusion may be called / an Army) & from a member of the Provincial / Congress that is now setting at Watertown. By / them I learn that an Army consisting of / 30,000 effective men is speedily to be raised in / the four New England Governments, & that the / quota for this Province is 13600. That as soon / as this Army shall be raised & regulated, it is / generally supposed that the first movement / will be to make a feint attack upon the Town / of Boston & at the same time to attempt the / Castle with the main body of the Army- / Whether this will be the precise plan of operation

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operation or not I cannot determine, but really / believe that the congress & their officers in Gene- / ral are determined to, & really imagine that they / shall be masters of both the Castle & the Town / of Boston in a very short time- / I am credibly informed that the Congress / mean now to prosecute their plan of Independence / at all adventures & in order to this that appli- / cation will speedily be made to someone of / the European Powers for assistance against Great / Britain- And this I am the moreready to / believe as I have it from a member of the congress, / one who is intimately acquainted with / the secrets of the party, & a man whom I can not / suspect of any design either to amuse or deceive / me. [page loss] / But this their plan is by no means [generally-?] / comonly known or suspecte by the People in gene / -ral, but they are still fed up with the old story / that "their invaluable rights & priviledges are / "invaded". & are taught to believe that the military / preparations which are now making are in defence / of them & to obtain redress- / As to the quantity of ordnances other military / stores that have been provided by the Congress & / I have not been able to obtain any satisfactory / accounts. But believe that the quantity is by no means equal.

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[page loss] plan of operation they have formed [page loss] / [page loss] [D]unbar from Canada, & Ens. Hamilton of / [page loss] Reg [?] with their servants are Prisoners in this / Town, But I have not permitted to see them tho[page loss] I / have made frequent applications for that purpose [page loss] / As to my own situation, it has been very disagreeable / since I left Boston, as upon my refusing to bear Arms a- / gainst the king I was more than ever suspected by the / People in this part of the Country [page loss] And it has been / with difficulty [page loss] few friends that I have here / have more than once prevented my bein asassinated. / I am extremely unhappy that my confinement to / this Town (by this deluded people) should put it out [page loss] / power to do any thing for the good of the service But [page loss] / soon to have an opportunity of giving convincing [page loss] / of my Loyalty to the King, & gratitude to all my benefac- / tors [page loss] in the mean time you will give me leave to as- / sure you in the most solemn manner possible, that neither / the threats nor promises of this wicked & Rebellious faction / shall ever induce me to do any thing contrary to my / professed loyalty to his Majesty [page loss] But that on the contrary / I do with the greatest pleasure & alacrity dedicate my / Life & fortune to the service of my rightful sovereign / King George the third - / I am Sir with the greatest respect / Your much obliged and / Most obedient Servant / [name cut out] / P.S. [name cut out] comes on purpose / to bring this & the Pistol you was kind / enough to lend me [page loss] I beg you would / be so good as to procure him a pass to / return

When looking at this letter, consider the following questions:

  • What was going on in the North American colonies when this letter was written? (Hint: the letter was written on May , 1775).
  • Why would invisible ink be useful during times of war? 
  • What is the invisible message saying? What is the visible message saying? Why might there be differences between the two?
  • This letter is to "an unknown recipient." Why do you think that is? Can you guess what kind of person received this letter?


Invisible ink was one of the more popular spy techniques and was achieved by writing the secret information between the lines of an otherwise standard letter using a special ink. Depending on the ink used, a chemical reagent or heat could reveal the secret code.

This letter was most likely written by Benjamin Thompson, who was an American-born soldier in the British Army.