Indeed, in the period of decolonization nationalism and anti-colonial or anti-imperialism were closely connected. Here’s how their relationship can be defined:

Non-Self-Governing Territories And The Question Of Nationalist Movements As Anti-Colonialism

-Common Purpose: Both sought to liberate colonised people from subjugation by their colonial masters, and achieve autonomous rule.
-Moral Framework: The authoritative raison d’être and the intellectual rationale for the nationalist struggles were provided by the anti-colonial ideology, arguing about the right of nations on self-determination.
-Mobilization Tool: They employed anti-colonial ideas in rallying people, towards occasioning solidarity and fighting colonial occupation.

Nationalism was a major influence of anti colonialism.

-Shared Identity: The colonial nationalist movements instilled the concept of unity, belonging and identity among the colonised people hence uniting them for their common cause that was against colonialism.
-Resistance Tactics: Nationalist movements used actions of civil disobedience, boycotts and guerrilla warfare all because of colonialism.
-International Solidarity: Nationalists’ movements teamed up with other anti-colonial movements that formed an anti-colonial international.

Some examples of connectedness Enlightenment.

-Indian National Movement: Mahatma Gandhis strategy of civil disobedience was thus based on the value of Indian nationalism and more generally anti-colonial logics.
-African National Congress (ANC): The ANC campaign against apartheid in South Africa was as nationalist as it was an anti-colonial struggle from the strength of the global anti-colonial campaigns.

Conclusion

Nationalism and anti-colonial or anti-imperialism ideologies encouraged each other. Nationalist movements provided an indexical and actual articulation to anti-colonial imaginations while anti-coloniality was a discursive frame for the organisation of resistance. All the above mentioned species in their own way contributed heavily to the process of decolonization and formation of new nation state entities.