When did the use of "Contact!" by soldiers emerge?

Question

I was recently watching a World War One docudrama-esque show (Our World War (BBC)) and, while patrolling and fighting to control Trones Wood, some British troops unexpectedly encounter the German enemy. Instinctively, a rifleman calls "contact" as the engagement begins.

Rightly or wrongly, the use of the phrase contact took me by surprise. It's a well known phrase and part of many Immediate Action drills in modern warfare, but it didn't strike me as one that would be in use during World War I.

For example, an American Vietnam Era combat handbook states:

This immediate action drill is used, defensively, to make and quickly break undesired but unavoidable contact (including ambush), and, offensively, to decisively engage the enemy (including ambush). When used in chance contact, men nearest the enemy open fire and shout, "Contact, Front (Right, Left, or Rear)." The patrol moves swiftly into line formation and assaults.

Source

So, my question is effectively twofold: When did the use of "Contact" begin and was the use in this context anachronistic?

Answer 1

According to the 1899 US Army French-English Military Technical Dictionary:

contact, m., touch, contact: (mil.) contact with the enemy

A 20 August 1898 US Army report from Puerto Rico says:

Being anxious to gain contact with the enemy, orders were given to move forward rapidly, and Lieutenant Heavey, with Company I, Eleventh Infantry, was left behind with instructions to repair the road, assist the ammunition wagons over, and to rejoin the command as quickly as possible.

There are many instances of "contact" being used for enemy contact in this document.

Well before this, the 1802 British A New and Enlarged Military Dictionary says:

I have seen, observes the Marshal, a whole volley of cool directed musquetry, occasion the loss of no more than four men ; while the troops against which it has been poured, have calmly marched up, reserved their fire till they got in contact with the enemy, and then amply revenged the deaths of their comrades by discharging their pieces, and following up with the bayonet.

Answer 2

From 1871 you have Helmuth von Moltke's famous quotation:

No plan of operations extends with any certainty beyond the first contact with the main hostile force.

At least, this is the usual way in which it is translated to English. Alternative translations for the original phrase could be encounter, meeting or conjuncture.

Von Moltke was a Chief of Staff rather than a simple rifleman but the phrase was definitely in use before the twentieth century.