The troubles of the Spanish war drove his parents to settle first at Veere in Zeeland, then to England, next at Rijwijk and lastly at Vlissingen.

There he studied under Joseph Scaliger, and there he met Marnix de St Aldegonde, Janus Dousa, Paulus Merula, Hugo Grotius and others; he was soon taken into the society of these celebrated men as their equal.

[1] His proficiency in the classical languages won the praise of all the best scholars of Europe, and offers were made to him, but in vain, to accept honourable positions outside Holland.

Through his ties with Naudé and others of the circle of De Thou then enjoying Papal favour, Heinsius began corresponding with Barberini’s protégés Giovanni Battista Doni, Professor of Greek at Florence, Bartolomeo Tortoletti, the poet and theologian, Baldassarre Bonifacio, honoured for his learning both in Rome and Venice, and Lucas Holstenius, a former student of Heinsius’ at Leiden, now in the Cardinal’s service.

Heinsius first drew attention to himself as a Latin poet with his Senecan tragedy Auriacus, sive libertas saucia ("William of Orange, or Freedom Wounded").

By 1628 he had contributed a Latin poem praising the renowned fencer Gerard Thibault to the front of his book Academie de L'espee.

They were greatly admired by Martin Opitz, who, in translating the poetry of Heinsius, introduced the German public to the use of the rhyming alexandrine.

In these years, he also wrote a large didactic poem, De contemptu mortis ("On the contempt of death", 1621), which has a Christian-Stoical content.