Lorenzo was involved in a revolt against the Spanish viceroy in Naples, and the family was forced to seek asylum in France around the time of Henri's birth.

For the following four years, De Tonti was commissioned into the French Navy as a midshipman, being stationed at Marseilles and Toulon and embarking on seven tours at sea, four of which were on tall ships and three on galleys.

This was a French army that Louis XIV sent to Sicily in 1675 under the command of the Duke of Vivonne to support the Messina revolt during the Franco-Dutch War.

Among the officers fighting beside the French expedition corps, there were the brothers Antonio and Thomas Crisafy, who years later de Tonti will have the chance to meet again in New France.

After the Franco-Dutch War, De Tonti was unable to obtain employment until recruited by La Salle, for exploration.

While on his return trip up the Illinois, La Salle concluded that Starved Rock might provide an ideal location for another fortification and sent word downriver to de Tonti regarding this idea.

Following La Salle's instructions, de Tonti took five men and departed up the river to evaluate the suitability of the Starved Rock site.

[8] This opened up opportunity for Iroquois warriors to attack, stabbing de Tonti and forcing his men to retreat to Baie-des-Puants in late 1680.

In the spring of 1682, de Tonti journeyed with La Salle on his descent down the Mississippi and helped establish alliances with Native Americans by presenting the calumet (a peace pipe) to the Natchez tribe, allowing La Salle to travel three leagues inland to meet with their chief.

La Salle departed for France in 1683 to gather colonists for a new Louisiana venture, leaving de Tonti behind to hold Fort St.

Denonville decided that war with Iroquois was inevitable, promising Illinois "every protection" as well as consultation from De Tonti on military excursions.

de Tonti and the others proceeded to their rendezvous on Lake Ontario and met up with Denonville and took part in the van of the French attack against the Senecas.

[6] De Tonti then commenced on a journey down the Mississippi to make contact with Pierre Le Moyne d'Iberville, who had established the Louisiana colony.

[3] Following this, De Tonti was offered by Pierre Moyne, Sieur d’Iberville the opportunity to work as a treaty negotiator and peacemaker.